Try matrix jobs

.github/workflows/build.yml

@@ -6,13 +6,28 @@ on:
       - master
 
 jobs:
-  build:
+
+  define-matrix:
     runs-on: ubuntu-latest
+    outputs:
+      hosts: $
+
     steps:
-      - uses: jlumbroso/free-disk-space@main
-        with:
-          large-packages: false
+      - uses: actions/checkout@v4
+
+      - name: Define hosts
+        run: |
+          hosts=[$(nix flake show --json | jq '.nixosConfigurations | keys[]' | paste -sd, -)]
+          echo "hosts=$hosts" >> $GITHUB_OUTPUT
 
+  build:
+    runs-on: ubuntu-latest
+    needs: define-matrix
+    strategy:
+      matrix:
+        host: ${{ fromJSON(needs.define-matrix.outputs.hosts) }}
+
+    steps:
       - uses: actions/checkout@v4
 
       - uses: cachix/install-nix-action@v27
@@ -27,13 +42,9 @@ jobs:
         with:
           name: joinemm
           authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
-
-      - name: build all hosts
+
+      - name: Build ${{ matrix.host }}
+        env:
+          host: ${{ matrix.host }}
         run: |
-          set -e
-          for host in `nix flake show --json | jq '.nixosConfigurations | keys[]'`; do
-            echo "--- Building configuration for \"$host\" ---"
-            nix build .#nixosConfigurations.$host.config.system.build.toplevel --no-link
-            nix-collect-garbage
-          done
-
+          nix build .#nixosConfigurations.$host.config.system.build.toplevel