Index: clang/lib/Driver/ToolChain.cpp
===================================================================
--- clang/lib/Driver/ToolChain.cpp
+++ clang/lib/Driver/ToolChain.cpp
@@ -929,8 +929,14 @@
   else if (LibName == "platform")
     return GetDefaultCXXStdlibType();
 
-  if (A)
-    getDriver().Diag(diag::err_drv_invalid_stdlib_name) << A->getAsString(Args);
+  if (A) {
+    static bool InvalidStdlibWarned = false;
+    if (!InvalidStdlibWarned) {
+      getDriver().Diag(diag::err_drv_invalid_stdlib_name)
+          << A->getAsString(Args);
+      InvalidStdlibWarned = true;
+    }
+  }
 
   return GetDefaultCXXStdlibType();
 }