release workflow: build pkghash executable

.github/workflows/release.yml

@@ -28,6 +28,14 @@ jobs:
       run: |
         echo "::set-output name=version::${GITHUB_REF#refs/tags/}"
 
+    - uses: goto-bus-stop/setup-zig@v2
+      with:
+        version: master
+    - name: Check zig version
+      run: zig version
+    - name: Build pkghash tool
+      run: zig build pkghash
+
     - name: Generate release notes
       id: release_notes
       run: |