Clang: Don't show a warning for unused macros anymore

Change-Id: Ia816476ed577d7060d752e74e5be2c2f1ebb7f12
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>

src/plugins/clangcodemodel/clangutils.cpp

@@ -207,6 +207,7 @@ private:
         add(QStringLiteral("-Weverything"));
         add(QStringLiteral("-Wno-c++98-compat"));
         add(QStringLiteral("-Wno-c++98-compat-pedantic"));
+        add(QStringLiteral("-Wno-unused-macros"));
         add(QStringLiteral("-fmessage-length=0"));
         add(QStringLiteral("-fdiagnostics-show-note-include-stack"));
         add(QStringLiteral("-fmacro-backtrace-limit=0"));