Select Xcode 16.3 in CI to get Swift 6.2+

Author: CraigStuntz

.github/workflows/ci.yml

@@ -12,6 +12,9 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      - name: Select Xcode 16.3
+        run: sudo xcode-select -s /Applications/Xcode_16.3.app
+
       - name: Build
         run: swift build