When installing the module, instead of copying the metainfo file to the
destination, merge the available translations for it. Since this is done
at install time, add gettext as BuildRequires for the RPM packaging;
add libappstream-glib-devel as well only on RHEL/CentOS 8, since it
contains the metainfo.its for gettext in order to handle .metainfo.xml
files.
This requires a LINGUAS file with the list of translations currently
available: this is the way msgfmt picks the available languages to
merge. Generate it dynamically from the list of available .po files.
The generated RPM is noarch, so by definition has no binaries to extract
debug symbols from. Hence, drop the %define that makes RPM not error out
in case there are no debug symbols around (usually in archful binaries).
