gdbus_codegen: Keep the same behavior for all GLib versions
gdbus_codegen: Keep the same behavior for all GLib versions

previous version duplicated the outputs disallowing to select only the .c files or the .h files
The docbook output files weren't listed too.

mesonbuild/meson,QuLogic/meson,mesonbuild/meson,mesonbuild/meson,mesonbuild/meson,thiblahute/meson,thiblahute/meson,jpakkane/meson,becm/meson,becm/meson,jpakkane/meson,becm/meson,mesonbuild/meson,pexip/meson,QuLogic/meson,mesonbuild/meson,jeandet/meson,pexip/meson,pexip/meson,MathieuDuponchelle/meson,mesonbuild/meson,thiblahute/meson,pexip/meson,becm/meson,QuLogic/meson,thiblahute/meson,thiblahute/meson,becm/meson,pexip/meson,mesonbuild/meson,jpakkane/meson,MathieuDuponchelle/meson,becm/meson,QuLogic/meson,QuLogic/meson,jpakkane/meson,jeandet/meson,thiblahute/meson,QuLogic/meson,MathieuDuponchelle/meson,jeandet/meson,pexip/meson,becm/meson,jeandet/meson,jeandet/meson,MathieuDuponchelle/meson,pexip/meson,jeandet/meson,MathieuDuponchelle/meson,pexip/meson,MathieuDuponchelle/meson,jeandet/meson,MathieuDuponchelle/meson,QuLogic/meson,mesonbuild/meson,jpakkane/meson,jpakkane/meson,jpakkane/meson,MathieuDuponchelle/meson,jpakkane/meson,pexip/meson,becm/meson,jpakkane/meson,jeandet/meson,becm/meson,QuLogic/meson,thiblahute/meson,pexip/meson,jeandet/meson,MathieuDuponchelle/meson,mesonbuild/meson,thiblahute/meson,thiblahute/meson,becm/meson,QuLogic/meson