This will be required for making a standalone, Nixery-style image
builder function usable from Nix.
Change-Id: I5e36348bd4c32d249d56f6628cd046916691319f
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5601
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>