I'm using pacman for my LFS install, and as part of that, I also use hooks used by Arch for, say, systemd-sysusers, systemd-tmpfiles, etc.
Some packages require that certain files/directories are owned by a certain user/group after install. This is somehow hard to achieve with .install file when systemd-sysuser hook is used (see  for an example).
Since this is a LFS, it's "bootstrapped" from an already existing linux distro (doesn't have to be arch, it has its own temporary pacman). I use pacman -U -r /path/to/lfs to install packages from the host system.
The issue I'm having is when an user isn't created and chown is ran in PKGBUILD's with statically assigned id's (ie, chown 20:20, where 20 will be an UID for the created user), pacman chowns those files/directories to something else entirely.
I did however notice that on my host (Arch, of course), those missleading uids/gids correspond to the uids/gids of the users that are going to be created in LFS.
So, if I have user/group named:named with uid:gid 20:20, and host system (Arch) has same user:group, with with uid:gid 40:40, the files that I explicitly chowned to 20:20 in PKGBUILD will be chown-ed to 40:40 instead when pacman -U -r ... is ran.
So, how do I solve this problem? I suppose it's an issue in pacman -U with -r option. I can use chown 20:20 in .install file (before the user:groups have been created), and the file will be created with proper ownership.
Thanks in advance.