It is now required to provide a resource compiler on windows when
compiling rust. This allows toolchain builders to explicitly provide a
path to an alternative, such as llvm-rc, instead of the one that's
provided by the Windows SDK.
Adds Windows resources with the rust version information to rustc-main.exe and rustc_driver.dll
Sets the product description to "Rust Compiler" or "Rust Compiler (channel)" for non-stable channels