cmake: Make it so that eglfs plugin doesn't hang on make -jN

Since the dependency on moc is in CorePrivate (o Core) we need
the target to depend on it otherwise cmake will try to use moc before
it is built.

This is because what we do with cmake is say "moc is in this
path, you can use it", but it's actually not built yet so
we need to depend on a target that depends on moc directly otherwise
cmake will trust us and try to use a cmake that doesn't exist and just
hang forever when running make -jN

Change-Id: Icf55c62092fd3fd3754a4f4f28c8c313bf374615
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/platforms/eglfs/CMakeLists.txt

@@ -90,6 +90,7 @@ add_qt_plugin(qeglfs
     INCLUDE_DIRECTORIES
         api
     LIBRARIES
+        Qt::CorePrivate
         Qt::EglFSDeviceIntegrationPrivate
         EGL::EGL
     # CONFIG = "egl"