llvm-ml: Error on MCSubtargetInfo construction failure (#159221)

Replace assert with an error.

Author: arsenm

llvm/tools/llvm-ml/llvm-ml.cpp

@@ -325,7 +325,10 @@ int llvm_ml_main(int Argc, char **Argv, const llvm::ToolContext &) {
 
   std::unique_ptr<MCSubtargetInfo> STI(
       TheTarget->createMCSubtargetInfo(TheTriple, /*CPU=*/"", /*Features=*/""));
-  assert(STI && "Unable to create subtarget info!");
+  if (!STI) {
+    WithColor::error(errs(), ProgName) << "unable to create subtarget info\n";
+    exit(1);
+  }
 
   // FIXME: This is not pretty. MCContext has a ptr to MCObjectFileInfo and
   // MCObjectFileInfo needs a MCContext reference in order to initialize itself.