Release 1.12.0

This is the first stable release in the 1.12.x series. The major changes
in this series is the support for better control of sub-sandboxes, as
used by the Steam Flatpak app to run Windows games under Proton.

In addition, this release fixes a security vulnerability in the portal
support. Some recently added syscalls were not blocked by the seccomp rules
which allowed the application to create sub-sandboxes which can confuse
the sandboxing verification mechanisms of the portal. This has been
fixed by extending the seccomp rules. (CVE-2021-41133)
For details, see:
GHSA-67h7-w3jq-vh4q

Other changes in this version:

• Some test fixes
• Update translations
• Support for specifying the flatpak binary to use during exports
• Install translations for all languages in the locale, not just the ones in
  LC_MESSAGES.
• Fix progress reporting in flatpak fsck
• Handle cases where /var/tmp is a symlink
• Expose /etc/gai.conf to the sandbox
• Fix the parental control checks for root
• Handle missing /etc/ld.so.cache (musl)

$ sha256sum flatpak-1.12.0.tar.xz 
d8a9a1f4cd1790711e836964eab6fb69de83b86c902249fff0c73706c73dd586  flatpak-1.12.0.tar.xz