Hardcoded unit tests to run on Xcode 16.4 on macos-15, due to breaking changes to macos image.

Author: w-goog

.github/workflows/unit_tests.yml

@@ -14,7 +14,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [macos-13]
+        os: [macos-latest]
         podspec: [GoogleSignIn.podspec, GoogleSignInSwiftSupport.podspec]
         flag: [
           "",
@@ -39,7 +39,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [macos-latest]
+        os: [macos-15]
         sdk: ['macosx', 'iphonesimulator']
         include:
           - sdk: 'macosx'
@@ -48,6 +48,8 @@ jobs:
             destination: '"generic/platform=iOS Simulator"'
     steps:
     - uses: actions/checkout@v3
+    - name: Select Xcode
+      run: sudo xcode-select -s /Applications/Xcode_16.4.app/Contents/Developer
     - name: Build unit test target
       run: |
         xcodebuild \