* New upstream release from the beta channel (THUNDERBIRD_30_0b1_BUILD2)
* Refresh patches
  - update debian/patches/unity-menubar.patch
  - update d/p/test-integration/xpcshell-disable-tests-which-need-appdir-write-access.patch
* Use --enable-system-libffi on arm64, as the bundled libffi doesn't
  support this yet
* Build with --enable-release option to use "more conservative, release
  engineering-oriented options" as recommended by upstream for distros:
  - Fixes FTBFS on powerpc and may improve stability on other arches.