Use systemd_user_unit_dir from systemd.pc, if found

[michel-slm]

If pkg-config can find systemd.pc (e.g. /usr/share/pkgconfig/systemd.pc), use its systemd_user_unit_dir for the location of psi-notify.service.

We override prefix to be whatever the user sets, which should work both for the distribution use case (prefix overridden to /usr) and for local compilation (prefix defaults to /usr/local)

Fall back to the old definition in case systemd.pc is not found.

Signed-off-by: Michel Alexandre Salim [email protected]

[michel-slm]

Tested using mock on my Fedora machine

• with this PR but no systemd.pc, a warning is generated
• with this PR and adding BR on pkgconfig(systemd), no warning

Both builds succeed as before

[cdown]

Sorry, this one somehow slipped off my radar :-)

systemd_user_unit_dir is from v246 onwards -- about two years old since we added it in addition to the non-underscore. So probably alright, but maybe use the one without underscores just to have wider compatibility? :-)

[cdown]

Been a bit, but just checking if you saw the compat question above :-)