build: remove -fuse-ld=bfd from LDFLAGS, unrecognized option

This option was improperly accepted previously despite being
unsupported. With GCC 4.7.x it is being explicitly rejected.
It isn't even needed because we do not use gold by default.
Merge pull request #18 from marineam/build

build: remove -fuse-ld=bfd from LDFLAGS, unrecognized option