OHTTP relay doesn't build #1246

This issue was reported by an OHTTP relay runner out-of-band.

seems like the image can't be built ATM anyways from the new repo AFAICT:

 => ERROR [builder 4/5] RUN nix     --extra-experimental-features "nix-command flakes"     --option filter-syscalls false     build                                                       0.9s
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 > [builder 4/5] RUN nix     --extra-experimental-features "nix-command flakes"     --option filter-syscalls false     build:                                                                  
0.147 path '/tmp/build/ohttp-relay' does not contain a 'flake.nix', searching up                                                                                                               
0.381 unpacking 'github:numtide/flake-utils/11707dc2f618dd54ca8739b309ec4fc024de578b?narHash=sha256-l0KFg5HjrsfsO/JpG%2Br7fRrqm12kzFHyUHqHCVpMMbI%3D' into the Git cache...
0.783 unpacking 'github:nix-systems/default/da67096a3b9bf56a91d16901293e51ba5b49a27e?narHash=sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768%3D' into the Git cache...
0.873 error: flake 'git+file:///tmp/build' does not provide attribute 'packages.aarch64-linux.default' or 'defaultPackage.aarch64-linux'
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Dockerfile.j2:9
--------------------
   8 |     # Build our Nix environment
   9 | >>> RUN nix \
  10 | >>>     --extra-experimental-features "nix-command flakes" \
  11 | >>>     --option filter-syscalls false \
  12 | >>>     build
  13 |     
--------------------
ERROR: failed to build: failed to solve: process "/bin/sh -c nix     --extra-experimental-features \"nix-command flakes\"     --option filter-syscalls false     build" did not complete successfully: exit code: 1

Tried on multiple architectures just to be sure

I'm guessing there are some changes needed to the Dockerfile you have (which is basically the same one I've been using) for this new structure