Add test for multiple overlays in G_RESOURCE_OVERLAY
As spotted in lrn/glib@fb644e9b (part of https://gitlab.gnome.org/lrn/glib/commits/w32-testsuite-fixes), there isn’t currently a test for multiple overlays being listed in G_RESOURCE_OVERLAY
. Such a test should be platform independent, using G_SEARCHPATH_SEPARATOR
rather than hard-coding a colon (:
).