Does this action support running with Alpine Linux docker?

[vadimkantorov]

I've done some attempts and it seems that it only fetches glibc-specific LLVM. If Alpine/musl isn't supported, it would be nice to have it mentioned in the README

[vadimkantorov]

Also would be good to have the action run some smoke tests, e.g. clang --version, emcc --version or OS check