Make the mingw toolchain accept 'ld' and 'lld' only as values to -fuse-ld.
Post-commit suggestion by Filipe Cabecinhas.

llvm-svn: 253161
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 436f640..3f07ad6 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -9468,6 +9468,8 @@
   if (LinkerName.equals_lower("lld")) {
     CmdArgs.push_back("-flavor");
     CmdArgs.push_back("gnu");
+  } else if (!LinkerName.equals_lower("ld")) {
+    D.Diag(diag::err_drv_unsupported_linker) << LinkerName;
   }
 
   if (!D.SysRoot.empty())