When building for baremetal targets, accept any arch that LLVM supports

Author: kubamracek

lib/Basic/LangOptions.cpp

@@ -389,7 +389,14 @@ std::pair<bool, bool> LangOptions::setTarget(llvm::Triple triple) {
     addPlatformConditionValue(PlatformConditionKind::Arch, "riscv64");
     break;
   default:
-    UnsupportedArch = true;
+    if ((Target.getOSName() == "none") &&
+        (Target.getArch() != llvm::Triple::ArchType::UnknownArch)) {
+      addPlatformConditionValue(
+          PlatformConditionKind::Arch,
+          llvm::Triple::getArchTypeName(Target.getArch()));
+    } else {
+      UnsupportedArch = true;
+    }
   }
 
   if (UnsupportedOS || UnsupportedArch)