Valgrind: Allow specifying extra arguments to valgrind etc

Fixes: QTCREATORBUG-18693
Change-Id: Ibb968dcd82b118340a45329b4a14b28d85700661
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/valgrind/valgrindengine.cpp

@@ -78,6 +78,7 @@ void ValgrindToolRunner::start()
 #endif
 
     CommandLine valgrind{m_settings.valgrindExecutable()};
+    valgrind.addArgs(m_settings.valgrindArguments(), CommandLine::Raw);
     valgrind.addArgs(genericToolArguments());
     valgrind.addArgs(toolArguments());