Install and force Xcode 16.4.0

Author: kelson42

.github/workflows/ci.yml

@@ -43,6 +43,14 @@ jobs:
         with:
           egress-policy: audit
 
+      - name: Install Xcode 16.6.0
+        uses: maxim-lobanov/setup-xcode@v1
+        with:
+           xcode-version: '16.4.0'
+
+      - name: Set Xcode version (15.0.1)
+        run: sudo xcode-select -s /Applications/Xcode_16.4.0.app
+
       - name: Checkout code
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2