internal: add caching to GitHub Actions (#2278)

.github/actions/pr_base/action.yml

@@ -66,6 +66,19 @@ runs:
         git commit -m "Merge PRs ${{inputs.DEPLOY_BRANCH}}"
       shell: powershell
 
+    - name: Get Current Git SHA
+      id: repo_sha
+      shell: powershell
+      run: |
+        $sha = git rev-parse HEAD
+        echo "sha=$sha" | Out-File -FilePath $Env:GITHUB_ENV -Encoding utf8 -Append
+
+    - name: Cache build dir
+      uses: actions/cache@v4
+      with:
+        path: ${{github.workspace}}/build
+        key: ${{ runner.os }}-skymp-${{ hashFiles('./build-metadata.json') }}-${{ env.sha }}
+
     - name: Early build skymp5-client
       run: |
         cd ${{github.workspace}}/skymp5-client