Avoid warning on empty expressions

For some reason, Q_UNUSED includes already a semicolon, adding one
on the user side creates an additional empty statement.

Change-Id: I9c5e8fac381345a60792cb75e2938fd53958d3b0
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/qmakeprojectmanager/addlibrarywizard.cpp

@@ -58,7 +58,7 @@ static bool validateLibraryPath(const Utils::FilePath &filePath,
                                 const Utils::PathChooser *pathChooser,
                                 QString *errorMessage)
 {
-    Q_UNUSED(errorMessage);
+    Q_UNUSED(errorMessage)
     if (!filePath.exists())
         return false;