postmarketOS image can be built with for example the following mkosi.local.conf:
```
[Distribution]
Distribution=postmarketos
[Output]
Format=disk
[Build]
UseSubvolumes=yes
[Runtime]
Firmware=uefi
```
This is analogous to a change in mkosi[1] with the same motivation: some
scripts are run to bootstrap the distribution tree and are thus running
directly on the host system which may not have `/bin/bash` (e.g. NixOS).
As with the `mkosi` change, do that for each shebang for consistency
reasons.
[1] https://github.com/systemd/mkosi/commit/8d2cd50e5192cada7211724ecff3514f0c85cf0f
If systemd-pcrphase-initrd.service and friends failed for some reasons,
the test VM will reboot infinitely and the test will timeout. Let's
propagate the failure to the host and fail the test earlier in that case.
Now that mkosi can automatically pick up its main configuration from
a mkosi/ subdirectory if it exists and there is no configuration in the
top level directory, let's make use of it to reduce the amount of clutter
in the top level directory of the repository.
This will also make it easier to install the mkosi configuration files as
part of the testing packages later on.
Yu Watanabe
Daan De Meyer
Maximilian Bosch
DaanDeMeyer