The path '/usr/share/appdata' is deprecated as is the .appdata.xml
extension, files should be in installed in '/usr/share/metainfo' with
a .metainfo.xml extension.
According to the docs, the metainfo path should be well supported even
by older distros like Ubuntu 16.04.
Reference: 2.1.2. Filesystem locations
https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html
It's the preferred location for system-provided plugins.
A compatible file in /etc is still kept. Also, the compatibility /etc
file needs to use a full path due to a bug in GNOME Shell.
The full path to a arch-dependent file in a supposedly arch-independent
file is a sin and a multilib violation in some distributions. However.
some pre-release versions of NetworkManager-1.2 as shipped by
distributions require a full path. Let's keep a configure-time option
for that.
This will ensure the strongSwan NetworkManager plugin will be easily
installable from the app stores such as GNOME Software.
Closesstrongswan/strongswan#41.