Fix slidingpopupstest when run without installtion

It tries to load scripted effects, so needs same adjustement.

autotests/integration/effects/slidingpopups_test.cpp

@@ -60,6 +60,7 @@ private Q_SLOTS:
 
 void SlidingPopupsTest::initTestCase()
 {
+    qputenv("XDG_DATA_DIRS", QCoreApplication::applicationDirPath().toUtf8());
     qRegisterMetaType<KWin::ShellClient*>();
     qRegisterMetaType<KWin::AbstractClient*>();
     qRegisterMetaType<KWin::Deleted*>();