nix: added cachix workflow

Author: lromor

.github/workflows/ci.yml

@@ -1,13 +1,11 @@
 name: ci
-
 on:
   push:
     branches:
-    - main
+      - main
   pull_request:
     branches:
-    - main
-
+      - main
 jobs:
   Test:
     runs-on: ubuntu-24.04
@@ -16,78 +14,65 @@ jobs:
         uses: actions/checkout@v4
         with:
           fetch-depth: 0
-
       - name: Create Cache Timestamp
         id: cache_timestamp
         uses: nanzm/get-time-action@v2.0
         with:
           format: 'YYYY-MM-DD-HH-mm-ss'
-
       - name: Mount bazel cache
         uses: actions/cache@v4
         with:
           path: "~/.cache/bazel"
           key: bazelcache_test_${{ steps.cache_timestamp.outputs.time }}
           restore-keys: bazelcache_test_
-
       - name: Test
         run: |
           export CC=gcc-13
           export CXX=g++-13
           bazel test --noshow_progress --keep_going ...
-
   MacOsBuild:
     runs-on: macos-latest
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
         with:
           fetch-depth: 0
-
       - name: Test
         run: |
           bazel test --noshow_progress --keep_going ...
-
       - name: Build
         run: |
           bazel build --noshow_progress -c opt //fpga:fpga-as
-
   CodeFormatting:
     runs-on: ubuntu-24.04
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
         with:
           fetch-depth: 0
-
       - name: Install Dependencies
         run: |
           sudo apt-get install clang-format-17
-
       - name: Run formatting style check
         run: |
           clang-format-17 --version
           RUNNING_IN_CI=1 CLANG_FORMAT=clang-format-17 \
             scripts/run-clang-format.sh
-
   ClangTidy:
     runs-on: ubuntu-24.04
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
         with:
           fetch-depth: 0
-
       - name: Install Dependencies
         run: |
           sudo apt-get install clang-tidy-18
-
       - name: Create Cache Timestamp
         id: cache_timestamp
         uses: nanzm/get-time-action@v2.0
         with:
           format: 'YYYY-MM-DD-HH-mm-ss'
-
       - name: Mount clang-tidy cache
         uses: actions/cache@v4
         with:
@@ -96,13 +81,24 @@ jobs:
             ~/.cache/bazel
           key: clang-tidy-cache_${{ steps.cache_timestamp.outputs.time }}
           restore-keys: clang-tidy-cache_
-
       - name: Build Compilation DB
         run: |
           scripts/make-compilation-db.sh
-
       - name: Run clang-tidy
         run: |
           clang-tidy-18 --version
           CLANG_TIDY=clang-tidy-18 scripts/run-clang-tidy-cached.cc \
             || ( cat fpga-assembler_clang-tidy.out ; exit 1)
+  NixBuild:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: cachix/install-nix-action@v25
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+      - uses: cachix/cachix-action@v15
+        with:
+          name: mycache
+          authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"
+      - run: nix-build
+      - run: nix-shell --run "echo OK"