gnome-settings uses pkgconfig to find gdesktop-enums.h https://github.com/GNOME/gnome-control-center/blob/4648296a706df83af984a918e5f14c3ece42f5fc/panels/background/meson.build#L22
Adding pc-sysrootdir to prefix would allow to find the file also if we have a user defined sysroot. This will fix cross compilation of gnome-control-center with yocto/openembedded that otherwise fails like this:
| ../gnome-control-center-43.2/panels/background/meson.build:27:0: ERROR: File /usr/include/gsettings-desktop-schemas/gdesktop-enums.h does not exist.
Signed-off-by: Markus Volk f_l_k@t-online.de