Use flatpak-spawn in flatpak

TODO

@@ -45,3 +45,5 @@ Better colors for vaapi. It looks a bit off when recording vscode for example.
 
 Clear vaapi surface (for focused window).
 Support -h and --help. -h should only show the first line and --help the full help. On error, only show that -h.
+
+Handle rotated monitor (on nvfbc and kms).