Respect XDG_CONFIG_HOME

[hadess]

rpm looks for .rpmmacros in ~/ but should probably look for an rpmmacros file in $HOME/.config instead.

From https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html:

$XDG_CONFIG_HOME defines the base directory relative to which user-specific configuration files should be stored. If $XDG_CONFIG_HOME is either not set or empty, a default equal to $HOME/.config should be used.

[pmatilai]

It's not a new idea nor a bad one, the last time it was proposed the whole XDG thing was so new I remember being wary whether this new thing'll actually catch on at all 😅

The "problem" is that rpmrc and macros loading is handled as a simple PATH style construct which has no room for extra logic like checking one path only if the other didn't exist, but maybe it can be retrofitted there, and not a whole lot of damage would happen if we just included both in the load path.