Useful or not, from you.
libdeflate Support feature detection with Embarcadero C++ Free compiler

It based on Clang compiler: https://www.embarcadero.com/free-tools/ccompiler

Download link: BCC102.zip

That's a useful answer
Without any help

I haven't used this compiler before, and it doesn't appear to be commonly used. It also doesn't appear to be easily installable on Linux like apt-get install clang (presumably because it is closed source?). So I am not planning to test it myself. If you would like some things to be changed to support it anyway, then please submit a pull request.