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>

tests/auto/cplusplus/preprocessor/tst_preprocessor.cpp

@@ -180,10 +180,10 @@ public:
         Q_UNUSED(initialIncludes)
 #if 1
         m_recordedIncludes.append(Include(includedFileName, mode, line));
-        Q_UNUSED(m_env);
-        Q_UNUSED(m_includeDepth);
+        Q_UNUSED(m_env)
+        Q_UNUSED(m_includeDepth)
 #else
-        Q_UNUSED(line);
+        Q_UNUSED(line)
 
         QString resolvedFileName;
         if (mode == IncludeLocal)