With glib < 2.51.3, gdbus-codegen does not understand "--output-directory" [1].
Hence, the generated files are like
"build/dbus-org.freedesktop.NetworkManager.Device.WifiP2P.xml"
instead of
"build/introspection/dbus-org.freedesktop.NetworkManager.Device.WifiP2P.xml"
But gnome.gdbus_codegen() returns a path as if it would be inside
"build/introspection". Hack around that, by patching the correct path
otherwise. This is still ugly, because repeated "ninja -C build" calls
will always try to rebuild this target (because the wrong file name
is considered).
See also [2].
[1] ee09bb704f
[2] 2e93ed58c3/mesonbuild/modules/gnome.py (L1170)
ad9e5995e1