autotests: Force OpenGL compositing in testPointerInput

Window View effect requires OpenGL compositing.

autotests/integration/pointer_input.cpp

@@ -149,6 +149,7 @@ void PointerInputTest::initTestCase()
     }
     qputenv("XCURSOR_SIZE", QByteArrayLiteral("24"));
     qputenv("XKB_DEFAULT_RULES", "evdev");
+    qputenv("KWIN_COMPOSE", QByteArrayLiteral("O2"));
 
     kwinApp()->start();
     QVERIFY(applicationStartedSpy.wait());