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The files:
'http.c',
'user_share-private.c',
'user_share-webdav.c'

Didn't touch any header from gio-unix-2.0.
Only 'share-extension.c' did.

When building gnome-user-share in Fedora, gnome-user-share-webdav.service
ends up incorrectly placed in /usr/lib64/systemd/user. It should be in
/usr/lib/systemd/user.

This is caused by us building a path from scratch, so that the prefix
could be overridden when doing an installation into a staging directory,
as the path supplied in systemd's pkgconfig file was broken in this
regard. This was however fixed in:
https://github.com/systemd/systemd/issues/9595
so use this instead.

Closes: #22

(cherry picked from commit 87a5d88f)