Add Nix package to new Zig compiler

[Hasnep]

This adds a Nix package for the new Zig based compiler to the Nix flake in src/, it can be tested by running

nix run github:hasnep/roc/add-nix-packages-for-new-compiler?dir=src

This will build the compiler package using Nix and run it.

[Anton-4]

Looks like this is ziglang/zig#20976

Prepare all required actions
Run ./.github/actions/flaky-retry
Run attempt=1
Attempt 1 of 4
Running command: nix build ./src/#roc && ./result/bin/roc check src/PROFILING/bench_repeated_check.roc
this derivation will be built:
  /nix/store/5j70vyv6kzh4ijhbfwrwswkwivg6nkpb-roc.drv
this path will be fetched (0.00 MiB download, 0.00 MiB unpacked):
  /nix/store/999ilh77rzjg38y3cpbg780b99bbjznc-zig-hook
copying path '/nix/store/999ilh77rzjg38y3cpbg780b99bbjznc-zig-hook' from 'https://cache.nixos.org/'...
building '/nix/store/5j70vyv6kzh4ijhbfwrwswkwivg6nkpb-roc.drv'...
error: builder for '/nix/store/5j70vyv6kzh4ijhbfwrwswkwivg6nkpb-roc.drv' failed with exit code 1;
       last 15 log lines:
       > Running phase: unpackPhase
       > unpacking source archive /nix/store/pqk46pzvp5rpqghhfd09gwzp1c99qgg9-g9y6lgai98rm7jpi4zl681mb5casyglg-source
       > source root is g9y6lgai98rm7jpi4zl681mb5casyglg-source
       > Running phase: patchPhase
       > Running phase: updateAutotoolsGnuConfigScriptsPhase
       > Running phase: configurePhase
       > no configure script, doing nothing
       > Running phase: buildPhase
       > zig build flags: -j4 -Dcpu=baseline --release=safe
       > /build/g9y6lgai98rm7jpi4zl681mb5casyglg-source/build.zig.zon:52:20: error: unable to discover remote git server capabilities: TemporaryNameServerFailure
       >             .url = "git+https://github.com/rdunnington/bytebox#5c8753ba11c394e4d642dddbb459edcd7c97ac26",
       >                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
       > /build/g9y6lgai98rm7jpi4zl681mb5casyglg-source/build.zig.zon:56:20: error: unable to discover remote git server capabilities: TemporaryNameServerFailure
       >             .url = "git+https://github.com/allyourcodebase/zstd.git#01327d49cbc56dc24c20a167bb0055d7fc23de84", // 1.5.7
       >                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
       For full logs, run:
         nix log /nix/store/5j70vyv6kzh4ijhbfwrwswkwivg6nkpb-roc.drv
Command failed with exit code 1 and error output contains 'TemporaryNameServerFailure'
Retrying...

[Anton-4]

nix build ./src/#roc is taking 12 minutes on macOS 15, while zig build -Dfuzz -Dsystem-afl=false -Doptimize=ReleaseFast only takes 5 minutes outside of nix.

[Hasnep]

I believe the slow build was because Nix was spending a long time copying files it didn't need to, I've added the Nix gitignore input to easily use the .gitignore files to reduce the files copied, and the build is taking 5 minutes for me now.