Configured storing Nx cache in GHA to speed up builds

refs https://github.com/TryGhost/DevOps/issues/47

- this allows us to store and restore the cache for TS builds, which
  should speed up the whole process

.github/workflows/ci.yml

@@ -20,6 +20,10 @@ env:
     ~/.cache/ms-playwright/
   CACHED_BUILD_PATHS: |
     ${{ github.workspace }}/ghost/*/build
+  NX_CACHE_RESTORE_KEYS: |
+    nx-Linux-${{ github.ref }}-${{ github.sha }}
+    nx-Linux-${{ github.ref }}
+    nx-Linux
 
 concurrency:
   group: ${{ github.head_ref || github.run_id }}
@@ -100,7 +104,7 @@ jobs:
       changed_any_code: ${{ steps.changed.outputs.any-code }}
       base_commit: ${{ env.BASE_COMMIT }}
       is_canary_branch: ${{ github.event_name == 'push' && (github.ref == 'refs/heads/main' || github.ref == 'refs/heads/arch') }}
-      is_git_sync: ${{ github.head_ref == 'main' || github.ref == 'refs/heads/main' }}
+      is_main: ${{ github.ref == 'refs/heads/main' }}
 
   job_install_deps:
     name: Install Dependencies
@@ -117,6 +121,14 @@ jobs:
         id: compute_lockfile_hash
         run: echo "hash=${{ hashFiles('yarn.lock') }}" >> "$GITHUB_OUTPUT"
 
+      - name: Nx cache
+        uses: actions/cache@v3
+        id: cache_nx
+        with:
+          path: .nxcache
+          key: nx-Linux-${{ github.ref }}-${{ env.HEAD_COMMIT }}
+          restore-keys: ${{needs.job_get_metadata.outputs.is_main == 'false' && env.NX_CACHE_RESTORE_KEYS || 'nx-never-restore'}}
+
       - name: Check dependency cache
         uses: actions/cache@v3
         id: cache_dependencies

.gitignore

@@ -48,6 +48,9 @@ typings/
 # Optional npm cache directory
 .npm
 
+# Nx cache
+.nxcache
+
 # Optional eslint cache
 .eslintcache
 

nx.json

@@ -8,7 +8,8 @@
                     "lint",
                     "test",
                     "test:unit"
-                ]
+                ],
+                "cacheDirectory": ".nxcache"
             }
         }
     },