frames: Load libadwaita on GNOME
Or, optionally, when the MUTTER_FRAMES_PLATFORM_LIBRARY env var is set to "adwaita". For debugging purposes, it is possible to disable loading any platform library with MUTTER_FRAMES_PLATFORM_LIBRARY set to "none".
Add the CSS class "ssd-frame" to the MetaFrame (i.e. GtkWindow) instances as that lets libadwaita pick the right style, and won't do anything for non-Adwaita styles.
This patch is specially careful not to link against libadwaita.
Closes #2830 (closed)
This is an alternative to !3015 (closed) that doesn't make mutter-x11-frames link against libadwaita.
This is how it looks on GNOME 47.beta and libadwaita!1257 (merged):
Edited by Georges Basile Stavracas Neto