Use a simpler predicate. NFC.

llvm-svn: 215218

llvm/tools/llvm-size/llvm-size.cpp

@@ -731,8 +731,7 @@ int main(int argc, char **argv) {
     if (ArchFlags[i] == "all") {
       ArchAll = true;
     } else {
-      Triple T = MachOObjectFile::getArch(ArchFlags[i]);
-      if (T.getArch() == Triple::UnknownArch) {
+      if (!MachOObjectFile::isValidArch(ArchFlags[i])) {
         outs() << ToolName << ": for the -arch option: Unknown architecture "
                << "named '" << ArchFlags[i] << "'";
         return 1;