[build] Repack wheel with maximum DEFLATE compression

Add a post-build step to recompress the wheel at compresslevel=9
(default is 6) to reduce artifact size.

Author: Breakthrough

.github/workflows/build_wheels_windows.yml

@@ -177,6 +177,30 @@ jobs:
         python setup.py $SKIP_CMAKE bdist_wheel --py-limited-api=cp37 --dist-dir="$PWD\wheelhouse" -v
       shell: pwsh
 
+    - name: Repack wheel with maximum compression
+      run: |
+        python -c "
+        import zipfile, os
+        method = zipfile.ZIP_DEFLATED
+        whl_dir = 'wheelhouse'
+        for name in os.listdir(whl_dir):
+            if not name.endswith('.whl'):
+                continue
+            src = os.path.join(whl_dir, name)
+            dst = src + '.tmp'
+            src_size = os.path.getsize(src)
+            print(f'Repacking {name} ({src_size / 1e9:.2f} GB)...')
+            with zipfile.ZipFile(src, 'r') as zin, zipfile.ZipFile(dst, 'w', method, compresslevel=9) as zout:
+                for item in zin.infolist():
+                    item.compress_type = method
+                    zout.writestr(item, zin.read(item.filename))
+            dst_size = os.path.getsize(dst)
+            saved = src_size - dst_size
+            print(f'Done: {dst_size / 1e9:.2f} GB (saved {saved / 1e6:.1f} MB, {100*saved/src_size:.1f}%)')
+            os.replace(dst, src)
+        "
+      shell: bash
+
     - name: Save build artifacts to cache
       uses: actions/cache/save@v3
       if: ${{ inputs.save_build_cache && !inputs.rolling_build }}