macOS: add option to choose compiler and investigate whether to make Clang the default one
In some testing with the EAGLE model and the use_dll
option it seems that Apple's Clang compiler (under x86_64 Rosetta with the default flags) is faster than Homebrew's GCC compiler with our optimized choice of flags. This requires some more testing to decide whether to make it the default and/or even improve the choice of flags for Clang. Either way, it would be good to have an option to choose the compiler, because as of preprocessor!79 (closed) we prioritize GCC and use Clang only as a fallback.