for some reason I don't got your reply but I read it throught the web interface.
I think the real error is
In file included from /usr/include/bits/errno.h:25:0,
                 from /usr/include/errno.h:36,
                 from ../../../zlib/zutil.h:38,
                 from ../../../zlib/crc32.c:29:
/usr/include/linux/errno.h:4:23: fatal error: asm/errno.h: No such file or directory
compilation terminated.
make[5]: *** [libz_a-crc32.o] Error 1
make[5]: Leaving directory `/home/maartenvd1994/gdc_building/gdc/dev/gcc4.6.1/objdir/64/zlib'
make[4]: *** [multi-do] Error 1
make[4]: Leaving directory `/home/maartenvd1994/gdc_building/gdc/dev/gcc-4.6.1/objdir/zlib'
make[3]: *** [all-multi] Error 2
make[3]: Leaving directory `/home/maartenvd1994/gdc_building/gdc/dev/gcc-4.6.1/objdir/zlib'
make[2]: *** [all-stage1-zlib] Error 2
make[2]: *** Waiting for unfinished jobs....

I'll recompile and save the output to a file and post it here.