Nixpkgs Optimized Compilation: march and mtune effects on compilers

I came across the wiki article describing how to apply optimizations for certain architectures to package rebuilds.

Using the current snippet:

nixpkgs.localSystem = {
  gcc.arch = "znver3";
  gcc.tune = "znver3";
  system = "x86_64-linux";

I can see the march and mtune flags being passed to builds. But so far I have only seen gcc builds. I am wondering if using the code snippet above, these optimizations will be applied to clang/llvm builds. For example: will Rust programs be compiled with the znver3 optimizations? What about other languages with different compilers?

These settings have gcc in the name, so I would like to know if further action needs to be taken to have these optimizations applied to other compilers.