Add locale support

The ~/.var/app/org.mozilla.firefox/cache/mozilla/firefox directory
is properly used nowadays.

https://gitlab.com/fedora/sigs/flatpak/fedora-flatpaks/-/issues/47

container.yaml

@@ -2,11 +2,20 @@ flatpak:
     id: org.mozilla.firefox
     branch: stable
     runtime-name: flatpak-runtime
-    runtime-version: f40
+    runtime-version: f44
     packages:
         - firefox
+        - firefox-langpacks
     command: firefox
     rename-icon: firefox
+    add-extensions:
+        org.mozilla.firefox.Locale:
+            directory: share/runtime/locale
+            autodelete: true
+            locale-subset: true
+        org.mozilla.firefox.systemconfig:
+            directory: etc/firefox
+            no-autodownload: true
     finish-args: |-
         --share=ipc
         --share=network
@@ -16,7 +25,6 @@ flatpak:
         --socket=pcsc
         --env=KRB5CCNAME=KCM:
         --filesystem=/run/.heim_org.h5l.kcm-socket
-        --filesystem=~/.cache/firefox:create
         --filesystem=~/.mozilla:create
         --filesystem=home:ro
         --filesystem=xdg-download:rw
@@ -34,3 +42,10 @@ flatpak:
         --talk-name=org.freedesktop.Notifications
         --own-name=org.mpris.MediaPlayer2.firefox.*
         --own-name=org.mozilla.firefox.*
+    cleanup-commands: |
+        cd /app/lib64/firefox/langpacks
+        for f in *; do
+            l=`echo $f | sed -e 's/langpack-\([^-@]*\).*/\1/'`
+            rm -f $f
+            ln -sf ../../../share/runtime/locale/$l/$f .
+        done