Experiment: use Tweag's self-hosted runners (#2037)

* Use Tweag's self hosted runners for the CI

* Explicitely use find from nixpkgs#findutils in CI

It is not installed by default on our self-hosted runners.

---------

Co-authored-by: Yuriy Taraday <[email protected]>

.github/workflows/continuous-integration.yml

@@ -16,15 +16,12 @@ jobs:
     strategy:
       matrix:
         os:
-          - ubuntu-latest
-          - macos-latest
+          - [self-hosted, Linux, X64]
+          - [self-hosted, macOS, ARM64]
         rust_channel:
           - stable
         include:
-          - os: ubuntu-latest
-            system: x86_64-linux
-          - os: macos-latest
-            system: x86_64-darwin
+          - os: [self-hosted, macOS, ARM64]
             continue-on-error: true
 
     runs-on: ${{ matrix.os }}
@@ -33,56 +30,39 @@ jobs:
 
     steps:
 
-    - name: Free Disk Space (Ubuntu)
-      uses: jlumbroso/[email protected]
-      if: runner.os == 'Linux'
-      with:
-        # this might remove tools that are actually needed,
-        # if set to "true" but frees about 6 GB. Currently we don't seem to need
-        # this extra disk space
-        tool-cache: false
-
-        # we might turn some of those off to trade CI time for less space saving
-        # if this step turns out to be too slow
-        android: true
-        dotnet: true
-        haskell: true
-        large-packages: true
-        docker-images: true
-        swap-storage: true
-
     - name: Checking out the repository
       uses: actions/checkout@v4
       with:
         fetch-depth: 0
 
-    - name: Installing Nix
-      uses: cachix/install-nix-action@v30
-      with:
-        nix_path: nixpkgs=channel:nixos-unstable
-        extra_nix_config: |
-          experimental-features = nix-command flakes
-          accept-flake-config = true
+    - name: Install cachix
+      id: install_cachix
+      run: |
+        set -euo pipefail
+        cachix_path="$(nix build --print-out-paths --inputs-from . nixpkgs#cachix.bin)"
+        echo "cachixBin=${cachix_path}/bin/cachix" >> "$GITHUB_OUTPUT"
 
     - name: Setup Cachix
       uses: cachix/cachix-action@v15
       with:
+        cachixBin: ${{ steps.install_cachix.outputs.cachixBin }}
         name: tweag-nickel
         authToken: '${{ secrets.CACHIX_TWEAG_NICKEL_AUTH_TOKEN }}'
+        skipAddingSubstituter: true
 
     - name: Run all checks
       run: |
           # see https://github.com/NixOS/nix/issues/8949 for why we redirect to
           # an output file. Everything else is just capturing the error code
           # while still printing the logs
           set +e
-          nix flake check --print-build-logs > logs 2>&1
+          nix flake check --accept-flake-config --print-build-logs > logs 2>&1
           errcode=$?
           cat logs
           exit $errcode
 
     - name: Typecheck benchmarks
-      run: find core/benches -type f -name "*.ncl" -print0 | xargs -0 -I file nix run . -- typecheck file
+      run: nix shell --inputs-from . .#nickel-lang-cli nixpkgs#findutils --command find core/benches -type f -name "*.ncl" -exec nickel typecheck '{}' \;
 
   build-and-test-windows:
     name: "build-and-test (windows-latest, stable)"