pkgsrc bootstrap failure on debian/wheezy gcc-4.7

gcc -O2 -Wno-error -I/usr/include -Wno-error  -Wall -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Wno-uninitialized -Wreturn-type -Wcast-qual -Wpointer-arith -Wwrite-strings -Wswitch -Wshadow -Werror  -D_LARGEFILE_SOURCE -D_LARGE_FILES -D_FILE_OFFSET_BITS=64 -DDEF_UMASK=022 -I/home/manu/Projects/netbsd/pkgsrc/bootstrap/work/wrk/pkgtools/pkg_install/work/bzip2 -I/home/manu/Projects/netbsd/pkgsrc/bootstrap/work/wrk/pkgtools/pkg_install/work/libarchive/libarchive -I/home/manu/Projects/netbsd/pkgsrc/bootstrap/work/wrk/pkgtools/pkg_install/work/libfetch -DHAVE_NBCOMPAT_H=1 -I/home/manu/Projects/netbsd/pkgsrc/bootstrap/work/wrk/pkgtools/pkg_install/work/libnbcompat -I/usr/include -I. -D_LARGEFILE_SOURCE -D_LARGE_FILES -DINET6 -DFTP_COMBINE_CWDS -c ftp.c
ftp.c: In function 'unmappedaddr':
ftp.c:149:2: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
cc1: all warnings being treated as errors
*** Error code 1