actions: update environment

Signed-off-by: Nick Chan <[email protected]>

.github/workflows/build.yml

@@ -72,7 +72,7 @@ jobs:
             gnu_triple: aarch64-apple-darwin
             os: iphoneos
             minos: 7.0
-    runs-on: macos-12
+    runs-on: macos-15
     env:
       MBEDTLS_VERSION: 3.5.2
       READLINE_VERSION: 8.2
@@ -102,7 +102,7 @@ jobs:
 
       - name: Select correct Xcode
         run: |
-          sudo xcode-select -s /Applications/Xcode_14.2.app
+          sudo xcode-select -s /Applications/Xcode_16.2.app
 
       - name: Setup environment
         run: |