message: Fix error message in case of unsupported LLVM version
diff: #include "target_registry.h"
  #if ISPC_LLVM_VERSION < OLDEST_SUPPORTED_LLVM || ISPC_LLVM_VERSION > LATEST_SUPPORTED_LLVM
  -#error "Only LLVM 8.0 - 12.0 and 13.0 development branch are supported"
  +#error "Only LLVM 11.0 - 13.0 and 14.0 development branch are supported"
  #endif
  #if defined(_WIN32) || defined(_WIN64)
  