Ubuntu 20.04 only has Python 3.8, and because the 'truststore'
dependency requires at least Python 3.10, the AppImage package would
need to bundle CA certificates from 'certifi' to make HTTPS requests
work at all, which is quite an ugly workaround.
Unfortunately, as a side effect, building on Ubuntu 22.04 increases the
minimum required version of glibc from 2.31 to 2.35.
This fixes the following error when you launch the app with an emoji
font installed (e.g. Noto Emoji):
X Error of failed request: BadLength (poly request too large or internal Xlib length error)
Major opcode of failed request: 139 (RENDER)
Minor opcode of failed request: 20 (RenderAddGlyphs)
Serial number of failed request: 277
Current serial number in output stream: 300
This has been fixed[1] in libXft 2.3.5[2], but unfortunately Ubuntu
20.04 (which we currently use in the Linux CI workflow), still has
version 2.3.3, so we have to build it ourselves.
[1] https://gitlab.freedesktop.org/xorg/lib/libxft/-/merge_requests/12
[2] https://lists.freedesktop.org/archives/xorg-announce/2022-September/003209.html
