ghc-6.10.4: mark build as broken

The build calls ar(1) in a way the tool doesn't like:

    ar q cru .libs/libffi.a  src/debug.o src/prep_cif.o src/types.o src/raw_api.o src/java_raw_api.o src/closures.o src/x86/ffi64.o src/x86/unix64.o src/x86/ffi.o src/x86/sysv.o
    ar: creating cru
    ar: .libs/libffi.a: No such file or directory
    make[4]: *** [Makefile:717: libffi.la] Error 1

This may have become an issue after some recent binutils update; I'm not sure.