On: Rustc_codegen_GCC can now bootstrap rustc

[JoshTriplett]

lld is not 100% compatible with ld; switching to it usually works, but occasionally breaks the build of some software. That's especially true for complex cases involving linker scripts and unusual binary layouts with various sections. (Those cases also tend to be hard to debug.)

[wyldfire → JoshTriplett]

But it's really well tested for building llvm and clang, so that suits the use case this thread is focused on.