chores: use custom github runners

n.b. the runners should already have Nix installed

Author: yvan-sraka

.github/workflows/nix-build.yml

@@ -71,23 +71,6 @@ jobs:
           /nix/var/nix/profiles/default/bin/nix copy --to 's3://nix-postgres-artifacts?secret-key=/etc/nix/nix-secret-key' $OUT_PATHS
           EOF
           sudo chmod +x /etc/nix/upload-to-cache.sh
-      - name: Install nix
-        uses: cachix/install-nix-action@v27
-        if: ${{ github.secret_source == 'Actions' }}
-        with:
-          install_url: https://releases.nixos.org/nix/nix-2.29.1/install
-          extra_nix_config: |
-            substituters = https://cache.nixos.org https://nix-postgres-artifacts.s3.amazonaws.com
-            trusted-public-keys = nix-postgres-artifacts:dGZlQOvKcNEjvT7QEAJbcV6b6uk7VF/hWMjhYleiaLI=% cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
-            post-build-hook = /etc/nix/upload-to-cache.sh
-      - name: Install nix
-        uses: cachix/install-nix-action@v27
-        if: ${{ github.secret_source == 'None' }}
-        with:
-          install_url: https://releases.nixos.org/nix/nix-2.29.1/install
-          extra_nix_config: |
-            substituters = https://cache.nixos.org https://nix-postgres-artifacts.s3.amazonaws.com
-            trusted-public-keys = nix-postgres-artifacts:dGZlQOvKcNEjvT7QEAJbcV6b6uk7VF/hWMjhYleiaLI=% cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
       - name: Aggressive disk cleanup for DuckDB build
         if: matrix.runner == 'macos-latest-xlarge'
         run: |

nix/github-actions.nix

@@ -1,6 +1,18 @@
 { inputs, ... }:
+let
+  githubPlatforms = {
+    "x86_64-linux" = "large-linux-x86";
+    "aarch64-linux" = "large-linux-arm";
+    "aarch64-darwin" = "macos-latest-xlarge";
+  };
+in
 {
   flake.githubActions = inputs.nix-github-actions.lib.mkGithubMatrix {
-    checks = inputs.nixpkgs.lib.getAttrs [ "x86_64-linux" ] inputs.self.checks;
+    checks = inputs.nixpkgs.lib.getAttrs [
+      "x86_64-linux"
+      "aarch64-linux"
+      "aarch64-darwin"
+    ] inputs.self.checks;
+    platforms = githubPlatforms;
   };
 }