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/projectexplorer/extracompiler.cpp

@@ -376,13 +376,13 @@ QStringList ProcessExtraCompiler::arguments() const
 
 bool ProcessExtraCompiler::prepareToRun(const QByteArray &sourceContents)
 {
-    Q_UNUSED(sourceContents);
+    Q_UNUSED(sourceContents)
     return true;
 }
 
 Tasks ProcessExtraCompiler::parseIssues(const QByteArray &stdErr)
 {
-    Q_UNUSED(stdErr);
+    Q_UNUSED(stdErr)
     return {};
 }