>> ../../gcc-4.7.2/gcc/config/mips/gnu-user.h:94:309: warning: missing terminating " character [enabled by default]

> Can you check what’s in that file, in the build tree?  Presumably the
> LIB_SPEC patching in base.scm doesn’t work as expected.

#define LIB_SPEC "-L/nix/store/7ya3mh0987kmc9xkwxzapkpw4s4hzkz0-glibc-2.17/lib %{!static:-rpath=/nix/store/7ya3mh0987kmc9xkwxzapkpw4s4hzkz0-glibc-2.17/lib %{!static-libgcc:-rpath=/nix/store/n4blfp5bz6lvx9w9afn1i9c9v7akjnns-gcc-4.7.2/lib64 -rpath=/nix/store/n4blfp5bz6lvx9w9afn1i9c9v7akjnns-gcc-4.7.2/lib}} " "\