Clang: Provide include directory only for libclang

Only libclang has issues with the include directory
search therefore undefining include folders makes sense
only for libclang options builder.

Change-Id: Ie3f62f5f3a89503e6e0ab59e18889e92425c3abc
Reviewed-by: Marco Bubke <marco.bubke@qt.io>

src/plugins/clangtools/clangtoolruncontrol.h

@@ -77,7 +77,7 @@ private:
     void start() final;
     void stop() final;
 
-    AnalyzeUnits unitsToAnalyze(const QString &clangVersion);
+    AnalyzeUnits unitsToAnalyze();
     void analyzeNextFile();
 
     void handleFinished();