themes: Fix enumeration of cursors with srcdir != builddir
themes: Fix enumeration of cursors with srcdir != builddir

rgcjonas/adwaita-semidark,rgcjonas/adwaita-semidark,DoctorJellyface/gnome-themes-standard,Distrotech/gnome-themes-standard,Distrotech/gnome-themes-standard,DoctorJellyface/gnome-themes-standard,rgcjonas/adwaita-semidark,rgcjonas/adwaita-semidark