bug#53558: [PATCH 2/2] gnu: Borg: Update to 1.2.0.

[Leo Famulari]

On Tue, Feb 22, 2022 at 05:09:08PM -0500, Leo Famulari wrote:
> * gnu/packages/backup.scm (borg): Update to 1.2.0.
> [source]: Adjust the list of Cython files to rebuild. Remove an obsolete
> substitution. Delete the bundled xxhash. Blake2 is no longer bundled.
> [native-inputs]: Add python-dateutil.
> [inputs]: Add xxhash. Add python-msgpack-1.2. Remove libb2.
> [arguments]: Export BORG_LIBXXHASH_PREFIX to ensure the build script can find
> xxhash. Adjust the list of skipped tests and make the custom 'check' phase 
> honor
> tests?. Install some more documentation.

Pushed as 50ccffb89e3dbb71a415b9c84b955006fe44fe02