ci: ensure subprocess is executable in wheel job

cp -r does not preserve permissions, so subprocess lost its +x bit
before build_distrib zipped it into the wheel. The ZipInfo.from_file()
fix in a68d6b1 preserves whatever mode is on disk — but by the time
the wheel job copies files into cefpython3/, the permission was already
gone. Add chmod +x to match what the test job already does.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: linesight

.github/workflows/ci-linux.yml

@@ -159,7 +159,9 @@ jobs:
           path: build/artifacts/
 
       - name: Set up cefpython3 package
-        run: cp -r build/artifacts/. cefpython3/
+        run: |
+          cp -r build/artifacts/. cefpython3/
+          chmod +x cefpython3/subprocess
 
       - name: Build wheel
         run: python tools/build_distrib.py