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/memchecktool.cpp

@@ -220,6 +220,8 @@ QStringList MemcheckToolRunner::toolArguments() const
     if (m_withGdb)
         arguments << "--vgdb=yes" << "--vgdb-error=0";
 
+    arguments << Utils::QtcProcess::splitArgs(m_settings.memcheckArguments());
+
     return arguments;
 }