Update GitHub Actions to use macOS 15 and Xcode 26

Author: rudrankriyam

.github/workflows/swift.yml

@@ -8,12 +8,16 @@ on:
 
 jobs:
   build:
-
-    runs-on: macos-latest
+    runs-on: macos-15
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
+
+    - name: Select Xcode
+      run: sudo xcode-select -s /Applications/Xcode_26.0.app
+
     - name: Build
       run: swift build -v
+
     - name: Run tests
       run: swift test -v