Draft: OCI images

Test:

1. nix build .#oci-hm-2
2. gunzip -c result | docker load
3. docker run -it oci-hm-2:latest
4. home-manager switch --flake git+https://code.europa.eu/ecphp/devs-profile#default --impure

The issue:

admin@78ffc1d0ae72 ~ > home-manager switch --flake git+https://code.europa.eu/ecphp/devs-profile#default --impure
error: builder for '/nix/store/jb9c39a65i2s6paj6inwjx7crjywgky9-builder.pl.drv' failed with exit code 1;
       last 1 log lines:
       > bash: /nix/store/4vq3350zc6sqnibkqpgic2d6cvi1r9hq-substitute-all.sh: No such file or directory
       For full logs, run 'nix log /nix/store/jb9c39a65i2s6paj6inwjx7crjywgky9-builder.pl.drv'.
error: 1 dependencies of derivation '/nix/store/78475mfpp658v545gkg272rn7n719kqi-home-manager-path.drv' failed to build
error: 1 dependencies of derivation '/nix/store/25hrdnc9yszf341i6qvcf97rgx2wd9ka-man-paths.drv' failed to build
error: 1 dependencies of derivation '/nix/store/znriraamw19cjmwril7d72lx3v1wvxqg-home-manager-generation.drv' failed to build