bootctl: explicitly disable systemd chroot detection

[jeckersb]

Closes: #2486
Signed-off-by: John Eckersberg dev@eckersberg.com

[jeckersb]

Manually sanity checked this locally

$ bcvk to-disk --composefs-backend --bootloader systemd --filesystem ext4 localhost/bootc /tmp/test-disk.raw
[...]
Bootloader: systemd
Installing bootloader via systemd-boot
error: Installing to disk: Setting up composefs boot: Installing bootloader: Subprocess failed: ExitStatus(unix_wait_status(256))
Created "/tmp/.tmp5DSaKZ/boot/EFI".
Created "/tmp/.tmp5DSaKZ/boot/EFI/systemd".
Created "/tmp/.tmp5DSaKZ/boot/EFI/BOOT".
Created "/tmp/.tmp5DSaKZ/boot/loader".
Created "/tmp/.tmp5DSaKZ/boot/loader/keys".
Created "/tmp/.tmp5DSaKZ/boot/loader/entries".
Created "/tmp/.tmp5DSaKZ/boot/EFI/Linux".
Failed to open boot loader directory /tmp/.tmp5DSaKZ/usr/lib/systemd/boot/efi: No such file or directory

Getting image source signatures
Copying blob sha256:5f70bf18a086007016e948b04aed3b82103a36bea41755b6cddfaf10ace3c6ef
Copying blob sha256:db23b8ddf9563de352d71e94156e5981c8820ed5c8af0daadde0465a5135d78e
Copying blob sha256:876231501b0a5ce44f6409d992f0ad92db10e4255f0be70e4d9f58236485add5
Copying blob sha256:f789e923178efa9907c62461a3d6fa2bf734847ea4a767dac7d51d44b6b62aa1
Copying blob sha256:f294b7f2d0af161b65051e9699b45eca4829f6ec4ddfba3677f47d9ad605000d
Copying blob sha256:df841d1c4eafcdf08d4b6677d388da2fdc812789d6d3b93c8fe0bb507ad8dbd6
Copying blob sha256:5f70bf18a086007016e948b04aed3b82103a36bea41755b6cddfaf10ace3c6ef
Copying config sha256:4f6ad565fee406697c41d14dbf1662ae132c849be032be1d1d3b9053022b767c
Writing manifest to image destination
Error:
   0: SSH installation command failed with exit code: Some(1)

Location:
   crates/kit/src/to_disk.rs:593

not exactly the best error message, but better than no error at all