I've had some issues with compiling extension that didn't have a wheel(I was using an older python version needed to support older library versions) and being required to install clang and then some hard to debug header missing issues. But after reinstalling clang versions several times and removing rye caches manually it worked. Changing CC=gcc did try to use gcc which has other issues when compiling. I think a lot of this has to do with fundamental issues with compiled extensions in Python that happens on any package manager when you don't have wheels.