[Rpm-maint] RPM 4.20.0 ALPHA2 released!

[Michal Domonkos]

Here comes the second ALPHA snapshot fixing a couple of bugs found in the first
snapshot, as well as adding small new improvements, most notably:

* Proper, built-in debuginfo enablement logic (#2204)
* Support for a timestamp handling policy (a new %build_mtime_policy macro)
* Fixed scriptlet prepend/append when used with the BuildSystem tag (#3024)

For a complete list of changes, visit the draft release notes:

    https://rpm.org/wiki/Releases/4.20.0

Note that the Compatibility Notes section has been updated to cover the above
two features as well.

On behalf of the RPM team,

    Michal