* Fix 'distribution' fact for ArchLinux
Allow empty wasn't breaking out of the process_dist_files
loop, so a empty /etc/arch-release would continue searching
and eventually try /etc/os-release. The os-release parsing
works, but the distro name there is 'Arch Linux' which does
not match the 2.3 behavior of 'Archlinux'
Add a OS_RELEASE_ALIAS map for the cases where we need to get
the distro name from os-release but use an alias.
We can't include 'Archlinux' in SEARCH_STRING because a name match on its keys
but without a match on the content causes a fallback to using the first
whitespace seperated item from the file content as the name.
For os-release, that is in form 'NAME=Arch Linux'
With os-release returning the right name, this also supports the
case where there is no /etc/arch-release, but there is a /etc/os-release
Fixes#30600
* pep8 and comment cleanup
3eab636b3f