Hopefully faster testing on ubuntu

.github/workflows/check.yml

@@ -9,11 +9,29 @@ concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
   cancel-in-progress: true
 jobs:
-  tests:
+  tests-ubuntu:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-latest macos-latest]
+        os: [ubuntu-latest]
+    steps:
+    - uses: actions/checkout@v5
+    - uses: DeterminateSystems/nix-installer-action@20
+      with:
+        github-token: ${{ secrets.GITHUB_TOKEN }}
+    - uses: cachix/cachix-action@v16
+      with:
+        name: rde
+        authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
+        extraPullNames: rstats-on-nix, nix-community
+    - run: nix build .
+    - run: nix flake check . --all-systems
+    - run: nix develop -c Rscript test/test.R
+  test-darwin:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [macos-latest]
     steps:
     - uses: actions/checkout@v5
     - uses: DeterminateSystems/nix-installer-action@20