CppEditor: Filter out another GCC-only flag

Qt applications are built with "-mno-direct-extern-access" these days,
which throws off clang-tidy.

Change-Id: Ifaaef84f6da37a0abb7b7a68296723fa41b572a7
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

src/plugins/cppeditor/compileroptionsbuilder.cpp

@@ -900,6 +900,10 @@ void CompilerOptionsBuilder::evaluateCompilerFlags()
             continue;
         }
 
+        // GCC option that clang doesn't know.
+        if (option.contains("direct-extern-access"))
+            continue;
+
         // These were already parsed into ProjectPart::includedFiles.
         if (option == includeFileOptionCl || option == includeFileOptionGcc) {
             skipNext = true;