wkd_sync/archlinux-keyring-wkd-sync.service.in:
Replace use of explicit script location (i.e. /usr/bin) with
SCRIPT_TARGET_DIR placeholder.
Makefile:
Create WKD sync service file from input file, replacing the
SCRIPT_TARGET_DIR placeholder with $SCRIPT_TARGET_DIR.
wkd_sync/archlinux-keyring-wkd-sync.service -> wkd_sync/archlinux-keyring-wkd-sync.service.in:
This allows using the file as input file, where overriding keywords can
be done using sed.