Ignore -Wc++11-compat as we require C++11 actually

pollutes gcc bots logs https://circleci.com/gh/harfbuzz/harfbuzz/85395

src/hb.hh

@@ -121,6 +121,7 @@
 #pragma GCC diagnostic ignored "-Wpacked" // Erratic impl in clang
 #pragma GCC diagnostic ignored "-Wstrict-aliasing"
 #pragma GCC diagnostic ignored "-Wtype-limits"
+#pragma GCC diagnostic ignored "-Wc++11-compat" // only gcc raises it
 #endif
 
 #endif