I'm having trouble building GDC (taken from the gdc-4.7 branch on github) using gcc-4.7.1

After about 10-15 minutes it just bails out with this error

/Users/danielharper/gdc/objdir/./gcc/xgcc -B/Users/danielharper/gdc/objdir/./gcc/ -B/opt/gdc/i386-apple-darwin12.1.0/bin/ -B/opt/gdc/i386-apple-darwin12.1.0/lib/ -isystem /opt/gdc/i386-apple-darwin12.1.0/include -isystem /opt/gdc/i386-apple-darwin12.1.0/sys-include    -o zlib/uncompr.o -DHAVE_CONFIG_H -I . -I ../../../../gcc-4.7.1/libphobos/gcc -I../../../../gcc-4.7.1/libphobos/../zlib -g -O2  -m64 -c ../../../../gcc-4.7.1/libphobos/../zlib/uncompr.c
make[8]: *** No rule to make target `libdruntime/libgdruntime.a', needed by `libgphobos2.a'.  Stop.
make[8]: *** Waiting for unfinished jobs....
/Users/danielharper/gdc/objdir/./gcc/xgcc -B/Users/danielharper/gdc/objdir/./gcc/ -B/opt/gdc/i386-apple-darwin12.1.0/bin/ -B/opt/gdc/i386-apple-darwin12.1.0/lib/ -isystem /opt/gdc/i386-apple-darwin12.1.0/include -isystem /opt/gdc/i386-apple-darwin12.1.0/sys-include    -o zlib/zutil.o -DHAVE_CONFIG_H -I . -I ../../../../gcc-4.7.1/libphobos/gcc -I../../../../gcc-4.7.1/libphobos/../zlib -g -O2  -m64 -c ../../../../gcc-4.7.1/libphobos/../zlib/zutil.c
make[7]: *** [all-recursive] Error 1
make[6]: *** [all] Error 2
make[5]: *** [multi-do] Error 1
make[4]: *** [all-multi] Error 2
make[3]: *** [all-recursive] Error 1
make[2]: *** [all] Error 2
make[1]: *** [all-target-libphobos] Error 2
make: *** [all] Error 2

I'm not sure where to go from here, can anyone help?