libostree v2020.5

["Colin Walters" <walters verbum org>]

https://github.com/ostreedev/ostree/releases/tag/v2020.5

This release primarily fixes a regression in 2020.4 where the "readonly sysroot" changes incorrectly left the 
sysroot read-only on systems that started out with a read-only `/` (most of them, e.g. Fedora Silverblue/IoT 
at least)
Link: https://github.com/ostreedev/ostree/pull/2160/commits/33eeb7b9ebd858c0246a9155b7a64b9f8a258583

One thing *not* fixed in this release that also changed in 2020.4 is that if you were shipping an OS build 
with device trees before proper support landed in 2020.4, you may need to "ratchet" an upgrade process.  See 
the linked issue for ongoing discussion.
Link: https://github.com/ostreedev/ostree/issues/2154

There's some additions to the pull API to aid flatpak, and although it turns out those are likely to be 
obviated by https://github.com/ostreedev/ostree/pull/2167 - we will retain those options in the future.
Link: https://github.com/ostreedev/ostree/pull/2166

There were a few fixes to the man pages, and `ostree show` now displays the parent commit.

The default dracut config now enables reproducibility.
Link: https://github.com/ostreedev/ostree/pull/2170

On the "feature" side, there is a new `ostree admin unlock --transient`.  We expect this to be a foundation 
for further support for "live" updates.
Link: https://github.com/ostreedev/ostree/pull/2103/commits/f2773c1b55cdcc7eea0558e4f2505d4ecbd53d62

Finally, various CI improvements landed - more testing of FCOS in PXE/ISO, and most notably there's a large 
brand new test (written in Rust) that exercises a mix of `kill -9` and `reboot -ff` (immediate forced 
reboots) while upgrading.

```
Benjamin Gilbert (1):
      ci: test FCOS PXE and ISO install

Colin Walters (8):
      Post-release version bump
      remount: Still remount /sysroot writable if not configured ro
      tests/repo-finder: Explicitly commit empty dir
      ci: Fix ISO testing
      ci: Barf on unset umask
      Add "transient" unlock
      tests/inst: Add destructive test framework
      Release 2020.5

Jonathan Lebon (7):
      app: Fix various CLI metavariable names
      lib/deploy: Clean up kargs override handling
      lib/deploy: Avoid shadowing variable
      lib/deploy: Simplify deployment creation
      lib/cleanup: Drop unnecessary GEqualFunc cast
      lib/deploy: Drop unneccessary function arg
      lib/deploy: Clarify comment re. staging API

João Paulo Rechi Vita (1):
      dracut: Create reproducible images

Philip Withnall (2):
      pull: Improve formatting of pull options in documentation
      pull: Add summary-{,sig-}bytes options to ostree_repo_pull()

Stefan Agner (3):
      man: add glossary to main man page
      man: add missing options to the ostree-commit man page
      Show commit checksum of parent, if present

Stephen Lowrie (1):
      ci: add pxe-offline-install testiso scenario
```