# cd /usr/src/
# cd lib/libc
# make
cc -O2 -pipe  -I/usr/src/lib/libc/include -I/usr/src/lib/libc/../../include -I/usr/src/lib/libc/amd64 -DNLS  -D__DBINTERFACE_PRIVATE -I/usr/src/lib/libc/../../contrib/gdtoa -DINET6 -I/usr/obj/usr/src/lib/libc -I/usr/src/lib/libc/resolv -D_ACL_PRIVATE -DPOSIX_MISTAKE -I/usr/src/lib/libc/../../contrib/tzcode/stdtime -I/usr/src/lib/libc/stdtime -I/usr/src/lib/libc/locale -DBROKEN_DES -DPORTMAP -DDES_BUILTIN -I/usr/src/lib/libc/rpc -DYP -DNS_CACHING -DSYMBOL_VERSIONING -std=gnu99 -fstack-protector -Wsystem-headers -Werror -Wall -Wno-format-y2k -Wno-uninitialized -Wno-pointer-sign -c /usr/src/lib/libc/gen/elf_utils.c
cc1: warnings being treated as errors
/usr/src/lib/libc/gen/elf_utils.c: In function '__pthread_map_stacks_exec':
/usr/src/lib/libc/gen/elf_utils.c:72: warning: implicit declaration of function '_rtld_get_stack_prot'
*** Error code 1

Stop in /usr/src/lib/libc.