Remove binutils when not needed

I noticed that my attempt at unifying Rust for Windows x86_64/i686 failed because of the dependency on binutils, which hardcodes the architecture on Windows.

So, I tried to remove it (except for Linux), and it worked!

Rust managed to build for all our platforms even without binutils, and the filename for Windows x86_64/i686 became the same one.

Moreover, we don't pass specific parameters for macOS and Android (even though we use var/configure_opt), which made me wonder: are there projects that really need binutils on non-Linux platforms, except for NSIS (which needs the GNU assembler)?