[compiler-rt] [compiler-rt] allow removing libc dependency on Android (PR #152394)

[John Ericson via llvm-commits]

Ericson2314 wrote:

Great!

That example makes sense to me --- I agree the right thing to do with the flag is indeed to drop that builtin entirely. Anything that would use it will instead gets a link error. This, we'll know when building libc against such a builtins library that we neither make dubious assumptions about CPU features, nor reenter libc in dubious ways.

> and the resulting library has a different name from the regular `compiler-rt.builtins.a`

I am OK making the upstream build system do that if you prefer, but just so you know, we would probably keep the same name in Nixpkgs. We already use `-resource-dir` to carefully control when Clang sees what, and it is just easier to keep on doing that, than also patch Clang and/or LLVM to teach it about a new builtins filename.

https://github.com/llvm/llvm-project/pull/152394