quick fix to run archinstall and enable systemd services

[blzrosa]

• This fix issue: Failed to enable fstrim.timer error #3800

PR Description:

Just inserted a direct call to SysCommand instead of self.arch_chroot, with the flag --root={self.target}.
This fixed the issue, at least for me.

Tests and Checks

• [ X ] I have tested the code!
  

[correctmost]

There was a similar suggestion on the Arch GitLab: https://gitlab.archlinux.org/archlinux/packaging/packages/systemd/-/issues/54#note_322382

[btantlinger]

The fix partially works, in that I am able to get Arch installed using archinstall... but still seems like something is broken. If I arch-chroot into the system after the install and run my post-install script, any systemctl command is failing with:

Failed to connect to system scope bus via local transport: No data available

This worked before the systemd update.

[correctmost]

The fix partially works, in that I am able to get Arch installed using archinstall... but still seems like something is broken.

There's an underlying issue in systemd: systemd/systemd#39021

[YHNdnzj]

Note that I've updated the PR description to highlight it's not a systemd bug after all. arch-chroot needs to be fixed and the systemd change just revealed the flaw there.

[YHNdnzj]

This operates on a chroot in a way native to systemd tools and should be done regardless of arch-chroot working or not.

[Torxed]

We have to remember that we're on Arch Linux and the recommended way (by our own Wiki) is/was to configure the system using arch-chroot, generally speaking.

It's unfortunate that this issue happens, and we'll try to work around it.
But we wish to use native tooling with default values wherever possible and not use workarounds or too many custom parameters (again, if possible).