Well there was a few before GNU came along. Including versions of UNIX itself. It's just GNU was free, and then, because of contributions, became better. LLVM was originally something the emulation world was into. It meant your JIT could be cross platform. That how I encountered it. It became something for the permissive/coportates to fight GCC later. Having actual competition has made GCC better and it hasn't lost to Clang/LLVM. The closed stuff didn't really compete as much just lock people in so didn't have to.

Unix-like?