Stop asserting when a meaningless -std= flag is passed for a non-compilation

input kind; go back to silently ignoring the flag.

llvm-svn: 295122

clang/lib/Frontend/CompilerInvocation.cpp

@@ -1702,8 +1702,8 @@ static bool IsInputCompatibleWithStandard(InputKind IK,
       return true;
     break;
   default:
-    llvm_unreachable("Cannot decide whether language standard and "
-        "input file kind are compatible!");
+    // For other inputs, accept (and ignore) all -std= values.
+    return true;
   }
   return false;
 }

clang/test/Driver/unknown-std.S

@@ -0,0 +1,2 @@
+// RUN: %clang -std=c++11 %s -E -o /dev/null 2>&1 | FileCheck %s --allow-empty
+// CHECK-NOT: error