The link error: 

MacBook-Pro-de-Yann-Sionneau:NetBSD fallen$ ./build.sh -m milkymist -U -u kernel=GENERIC
===> build.sh command:    ./build.sh -m milkymist -U -u kernel=GENERIC
===> build.sh started:    Tue Oct  8 22:46:21 CEST 2013
===> NetBSD version:      6.99.16
===> MACHINE:             milkymist
===> MACHINE_ARCH:        lm32
===> Build platform:      Darwin 10.8.0 i386
===> HOST_SH:             /bin/sh
===> MAKECONF file:       /etc/mk.conf (File not found)
===> TOOLDIR path:        /Users/fallen/dev/NetBSD/obj/tooldir.Darwin-10.8.0-i386
===> DESTDIR path:        /Users/fallen/dev/NetBSD/obj/destdir.milkymist
===> RELEASEDIR path:     /Users/fallen/dev/NetBSD/obj/releasedir
===> Updated makewrapper: /Users/fallen/dev/NetBSD/obj/tooldir.Darwin-10.8.0-i386/bin/nbmake-milkymist
===> Building kernel without building new tools
===> Building kernel:     GENERIC
===> Build directory:     /Users/fallen/dev/NetBSD/sys/arch/milkymist/compile/obj/GENERIC
Build directory is /Users/fallen/dev/NetBSD/sys/arch/milkymist/compile/obj/GENERIC
Don't forget to run "make depend"
depending the kern library objects
depending the compat library objects
making sure the compat library is up to date...
`libcompat.a' is up to date.
making sure the kern library is up to date...
`libkern.o' is up to date.
#      link  GENERIC/netbsd
/Users/fallen/dev/NetBSD/obj/tooldir.Darwin-10.8.0-i386/bin/lm32--netbsd-ld -Map netbsd.map --cref -n -T /Users/fallen/dev/NetBSD/sys/arch/milkymist/conf/kern.ldscript -Ttext 0xc0000000 -e start -S -o netbsd ${SYSTEM_OBJ} ${EXTRA_OBJ} vers.o
/Users/fallen/dev/NetBSD/obj/tooldir.Darwin-10.8.0-i386/bin/lm32--netbsd-ld: section link_set_bufq_strats loaded at [00000000400fc4b0,00000000400fc4bb] overlaps section .data loaded at [00000000400fc4b0,000000004010288f]
/Users/fallen/dev/NetBSD/obj/tooldir.Darwin-10.8.0-i386/bin/lm32--netbsd-ld: warning: cannot find entry symbol start; defaulting to 00000000c0000000

*** Failed target:  netbsd
*** Failed command: echo '# ' " link GENERIC/netbsd"; echo /Users/fallen/dev/NetBSD/obj/tooldir.Darwin-10.8.0-i386/bin/lm32--netbsd-ld -Map netbsd.map --cref -n -T /Users/fallen/dev/NetBSD/sys/arch/milkymist/conf/kern.ldscript -Ttext 0xc0000000 -e start -S -o netbsd '${SYSTEM_OBJ}' '${EXTRA_OBJ}' vers.o; /Users/fallen/dev/NetBSD/obj/tooldir.Darwin-10.8.0-i386/bin/lm32--netbsd-ld -Map netbsd.map --cref -n -T /Users/fallen/dev/NetBSD/sys/arch/milkymist/conf/kern.ldscript -Ttext 0xc0000000 -e start -S -o netbsd locore.o devsw.o ioconf.o param.o autoconf.o bpf_stub.o bufq_disksort.o bufq_fcfs.o clock.o clock_subr.o cnmagic.o cons.o copy.o cpu.o dead_vnops.o debugsyms.o dk.o exec_subr.o fdesc_vfsops.o fdesc_vnops.o fifo_vnops.o genfs_io.o genfs_rename.o genfs_vfsops.o genfs_vnops.o if.o if_media.o init_main.o init_sysctl.o init_sysctl_base.o init_sysent.o interrupt.o intr.o kern_acct.o kern_auth.o kern_cfglock.o kern_clock.o kern_condvar.o kern_core.o kern_cpu.o kern_descrip.o kern_event.o kern_exec.o kern_exit.o kern_fork.o kern_hook.o kern_idle.o kern_kthread.o kern_lock.o kern_lwp.o kern_malloc.o kern_module.o kern_module_vfs.o kern_mutex.o kern_mutex_obj.o kern_ntptime.o kern_physio.o kern_pmf.o kern_proc.o kern_prot.o kern_ras.o kern_rate.o kern_resource.o kern_rndpool.o kern_rndq.o kern_runq.o kern_rwlock.o kern_rwlock_obj.o kern_sig.o kern_sleepq.o kern_softint.o kern_ssp.o kern_stub.o kern_subr.o kern_synch.o kern_syscall.o kern_sysctl.o kern_tc.o kern_time.o kern_timeout.o kern_todr.o kern_turnstile.o kern_uidinfo.o kern_uuid.o kern_xxx.o kernfs_subr.o kernfs_vfsops.o kernfs_vnops.o link_proto.o lock_stubs.o locore_subr.o machdep.o mainbus.o mfs_miniroot.o mm.o net_stats.o nist_ctr_drbg.o pmap.o process_machdep.o procfs_cmdline.o procfs_ctl.o procfs_fd.o procfs_fpregs.o procfs_linux.o procfs_machdep.o procfs_map.o procfs_mem.o procfs_note.o procfs_regs.o procfs_status.o procfs_subr.o procfs_vfsops.o procfs_vnops.o ptyfs_subr.o ptyfs_vfsops.o ptyfs_vnops.o quota1_subr.o radix.o raw_cb.o raw_usrreq.o rijndael-alg-fst.o rijndael-api-fst.o rijndael.o rndpseudo.o route.o rtbl.o rtsock.o sched_4bsd.o secmodel.o secmodel_bsd44.o secmodel_extensions.o secmodel_securelevel.o secmodel_suser.o sig_machdep.o spec_vnops.o subr_autoconf.o subr_blist.o subr_bufq.o subr_callback.o subr_copy.o subr_cprng.o subr_cpufreq.o subr_device.o subr_devsw.o subr_disk.o subr_disk_open.o subr_evcnt.o subr_exec_fd.o subr_extent.o subr_hash.o subr_humanize.o subr_iostat.o subr_kcpuset.o subr_kmem.o subr_kobj.o subr_kobj_vfs.o subr_lockdebug.o subr_log.o subr_lwp_specificdata.o subr_once.o subr_optstr.o subr_pcq.o subr_pcu.o subr_percpu.o subr_pool.o subr_prf.o subr_prof.o subr_pserialize.o subr_specificdata.o subr_time.o subr_vmem.o subr_workqueue.o subr_xcall.o sync_subr.o sync_vnops.o sys_aio.o sys_descrip.o sys_generic.o sys_lwp.o sys_machdep.o sys_module.o sys_mqueue.o sys_pipe.o sys_pmc.o sys_process.o sys_pset.o sys_sched.o sys_select.o sys_sig.o sys_socket.o syscall.o timer.o tmpfs_fifoops.o tmpfs_mem.o tmpfs_rename.o tmpfs_specops.o tmpfs_subr.o tmpfs_vfsops.o tmpfs_vnops.o tty.o tty_conf.o tty_ptm.o tty_pty.o tty_subr.o tty_tty.o uart.o uipc_accf.o uipc_domain.o uipc_mbuf.o uipc_mbuf2.o uipc_proto.o uipc_sem.o uipc_socket.o uipc_socket2.o uipc_syscalls.o uipc_usrreq.o uvm_amap.o uvm_anon.o uvm_aobj.o uvm_bio.o uvm_coredump.o uvm_device.o uvm_emap.o uvm_fault.o uvm_glue.o uvm_init.o uvm_io.o uvm_km.o uvm_loan.o uvm_map.o uvm_meter.o uvm_mmap.o uvm_mremap.o uvm_object.o uvm_page.o uvm_pager.o uvm_pdaemon.o uvm_pdpolicy_clock.o uvm_pglist.o uvm_readahead.o uvm_stat.o uvm_swap.o uvm_unix.o uvm_user.o uvm_vnode.o vfs_bio.o vfs_cache.o vfs_cwd.o vfs_dirhash.o vfs_getcwd.o vfs_hooks.o vfs_init.o vfs_lockf.o vfs_lookup.o vfs_mount.o vfs_quotactl.o vfs_subr.o vfs_syscalls.o vfs_trans.o vfs_vnode.o vfs_vnops.o vfs_xattr.o vm_machdep.o vnode_if.o /Users/fallen/dev/NetBSD/sys/arch/milkymist/compile/obj/GENERIC/lib/compat/libcompat.a /Users/fallen/dev/NetBSD/sys/arch/milkymist/compile/obj/GENERIC/lib/kern/libkern.o vers.o swapnetbsd.o
*** Error code 1

Stop.
nbmake: stopped in /Users/fallen/dev/NetBSD/sys/arch/milkymist/compile/obj/GENERIC

ERROR: Failed to make all in "/Users/fallen/dev/NetBSD/sys/arch/milkymist/compile/obj/GENERIC"
*** BUILD ABORTED ***

The linker script: 

OUTPUT_FORMAT("elf32-lm32")
ENTRY(_start)

__DYNAMIC = 0;

MEMORY {
        sdram : ORIGIN = 0xc0000000, LENGTH = 0x8000000
}

SECTIONS
{
        .text 0xc0000000 : AT ( 0x40000000 )
        {
                _ftext = .;
                *(.text .stub .text.* .gnu.linkonce.t.*)
                _etext = .;
        } > sdram

        .rodata ADDR(.text) + SIZEOF(.text) : AT ( LOADADDR(.text) + SIZEOF(.text) )
        {
                . = ALIGN(4);
                _frodata = .;
                *(.rodata .rodata.* .gnu.linkonce.r.*)
                *(.rodata1)
                _erodata = .;
        } > sdram

        /* We shouldn't have a .data section, however the GNU crapchain whines if we don't */
        .data : AT ( LOADADDR(.rodata) + SIZEOF(.rodata) )
        {
                . = ALIGN(4);
                _fdata = .;
                *(.data .data.* .gnu.linkonce.d.*)
                *(.data1)
                _gp = ALIGN(16);
                *(.sdata .sdata.* .gnu.linkonce.s.*)
               _edata = .;
        } > sdram

        .bss : AT ( LOADADDR(.data) + SIZEOF(.data) )
        {
                . = ALIGN(4);
                _fbss = .;
                *(.dynsbss)
                *(.sbss .sbss.* .gnu.linkonce.sb.*)
                *(.scommon)
                *(.dynbss)
                *(.bss .bss.* .gnu.linkonce.b.*)
                *(COMMON)
                . = ALIGN(4);
                _ebss = .;
                _end = .;
        } > sdram
}

PROVIDE(_fstack = ORIGIN(sdram) + LENGTH(sdram) - 4);
PROVIDE(_phy_do_real_tlb_miss_handling = _do_real_tlb_miss_handling - 0xc0000000 + 0x40000000);

Result of some commands:

MacBook-Pro-de-Yann-Sionneau:GENERIC fallen$ grep -Rsn "link_set_bufq_strats" *
Binary file bufq_disksort.o matches
Binary file bufq_fcfs.o matches
netbsd.map:8218:link_set_bufq_strats
netbsd.map:8221:                0x00000000c00fc4b0                PROVIDE (__start_link_set_bufq_strats, ABSOLUTE (.))
netbsd.map:8222: link_set_bufq_strats
netbsd.map:8224: link_set_bufq_strats
netbsd.map:8226: link_set_bufq_strats
netbsd.map:8228:                0x00000000c00fc4bc                PROVIDE (__stop_link_set_bufq_strats, .)
netbsd.map:16144:__start_link_set_bufq_strats                      subr_bufq.o
netbsd.map:16151:__stop_link_set_bufq_strats                       subr_bufq.o
Binary file subr_bufq.o matches

MacBook-Pro-de-Yann-Sionneau:NetBSD fallen$ cd sys/arch/milkymist/compile/obj/GENERIC/
MacBook-Pro-de-Yann-Sionneau:GENERIC fallen$ /Users/fallen/dev/NetBSD/obj/tooldir.Darwin-10.8.0-i386/bin/lm32--netbsd-nm *.o | grep "link_set_bufq"
00000000 r __link_set_bufq_strats_sym_bufq_strat_disksort
00000000 r __link_set_bufq_strats_sym_bufq_strat_fcfs
00000000 r __link_set_bufq_strats_sym_bufq_strat_dummy
         U __start_link_set_bufq_strats
         U __stop_link_set_bufq_strats


MacBook-Pro-de-Yann-Sionneau:NetBSD fallen$ grep -Rsn "link_set_bufq_strats" *
netbsd.S:266966:Disassembly of section link_set_bufq_strats:
netbsd.S:266968:c00fc4a0 <__link_set_bufq_strats_sym_bufq_strat_disksort>:
netbsd.S:266971:c00fc4a4 <__link_set_bufq_strats_sym_bufq_strat_fcfs>:
netbsd.S:266974:c00fc4a8 <__link_set_bufq_strats_sym_bufq_strat_dummy>:
Binary file sys/arch/milkymist/compile/obj/GENERIC/bufq_disksort.o matches
Binary file sys/arch/milkymist/compile/obj/GENERIC/bufq_fcfs.o matches
sys/arch/milkymist/compile/obj/GENERIC/netbsd.map:8218:link_set_bufq_strats
sys/arch/milkymist/compile/obj/GENERIC/netbsd.map:8221:                0x00000000c00fc4b0                PROVIDE (__start_link_set_bufq_strats, ABSOLUTE (.))
sys/arch/milkymist/compile/obj/GENERIC/netbsd.map:8222: link_set_bufq_strats
sys/arch/milkymist/compile/obj/GENERIC/netbsd.map:8224: link_set_bufq_strats
sys/arch/milkymist/compile/obj/GENERIC/netbsd.map:8226: link_set_bufq_strats
sys/arch/milkymist/compile/obj/GENERIC/netbsd.map:8228:                0x00000000c00fc4bc                PROVIDE (__stop_link_set_bufq_strats, .)
sys/arch/milkymist/compile/obj/GENERIC/netbsd.map:16144:__start_link_set_bufq_strats                      subr_bufq.o
sys/arch/milkymist/compile/obj/GENERIC/netbsd.map:16151:__stop_link_set_bufq_strats                       subr_bufq.o
Binary file sys/arch/milkymist/compile/obj/GENERIC/subr_bufq.o matches

FYI netbsd.S is what I got by doing objdump -D on netbsd ELF binary.