GCC support would only add backends for very obscure or borderline abandoned platforms, because everything else is either in the process of being merged into LL

GCC support would only add backends for very obscure or borderline abandoned platforms, because everything else is either in the process of being merged into LLVM (i.e. ESP32 Xtensa) or it's already supported. The main benefit of a GCC-based Rust compiler would be disentangling Rust from rustc, specification from implementation.