nix: Refactor gh-actions and re-enable nightly builds (#31489)

Now that the nix build is working again, re-enable nightly builds and
refactor the workflow for re-use between nightly releases and CI jobs.

Release Notes:

- N/A

---------

Co-authored-by: Rahul Butani <rrbutani@users.noreply.github.com>

.github/workflows/ci.yml

@@ -714,48 +714,12 @@ jobs:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
   nix-build:
-    timeout-minutes: 60
-    name: Nix Build
-    continue-on-error: true
+    uses: ./.github/workflows/nix.yml
     if: github.repository_owner == 'zed-industries' && contains(github.event.pull_request.labels.*.name, 'run-nix')
-    strategy:
-      fail-fast: false
-      matrix:
-        system:
-          - os: x86 Linux
-            runner: buildjet-16vcpu-ubuntu-2204
-            install_nix: true
-          - os: arm Mac
-            runner: [macOS, ARM64, test]
-            install_nix: false
-    runs-on: ${{ matrix.system.runner }}
-    env:
-      ZED_CLIENT_CHECKSUM_SEED: ${{ secrets.ZED_CLIENT_CHECKSUM_SEED }}
-      GIT_LFS_SKIP_SMUDGE: 1 # breaks the livekit rust sdk examples which we don't actually depend on
-    steps:
-      - name: Checkout repo
-        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
-        with:
-          clean: false
-      - name: Set path
-        if: ${{ ! matrix.system.install_nix }}
-        run: |
-          echo "/nix/var/nix/profiles/default/bin" >> $GITHUB_PATH
-          echo "/Users/administrator/.nix-profile/bin" >> $GITHUB_PATH
-
-      - uses: cachix/install-nix-action@d1ca217b388ee87b2507a9a93bf01368bde7cec2 # v31
-        if: ${{ matrix.system.install_nix }}
-        with:
-          github_access_token: ${{ secrets.GITHUB_TOKEN }}
-
-      - uses: cachix/cachix-action@0fc020193b5a1fa3ac4575aa3a7d3aa6a35435ad # v16
-        with:
-          name: zed-industries
-          authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"
-          skipPush: true
-      - run: nix build .#debug
-      - name: Limit /nix/store to 50GB
-        run: "[ $(du -sm /nix/store | cut -f1) -gt 50000 ] && nix-collect-garbage -d"
+    with:
+      flake-output: debug
+      # excludes the final package to only cache dependencies
+      cachix-filter: "-zed-editor-[0-9.]*-nightly"
 
   auto-release-preview:
     name: Auto release preview