Remove "systemduserunitdir" work-around
Code says:
enable_systemd = get_option('systemd')
if enable_systemd
systemd_dep = dependency('systemd', required: false)
assert(systemd_dep.found(), 'Systemd support explicitly required, but systemd not found')
# XXX: Once https://github.com/systemd/systemd/issues/9595 is fixed and we can
# depend on this version, replace with something like:
# systemduserunitdir = systemd_dep.get_pkgconfig_variable('systemduserunitdir')
# and uncomment systemd_dep below
systemd_userunitdir = join_paths(gsd_prefix, 'lib', 'systemd', 'user')
endif
https://github.com/systemd/systemd/issues/9595 is now fixed, so the variable can be used directly. Older versions of systemd will fail to install. gnome-user-share has a similar requirement and worked around potential problems by having a option about where to put those files.