Update build agent to macos-14

Also pin the Windows agent version.

Author: AArnott

.github/workflows/build.yml

@@ -22,8 +22,8 @@ jobs:
       matrix:
         os:
         - ubuntu-22.04
-        - macos-latest
-        - windows-latest
+        - macos-14
+        - windows-2022
 
     steps:
     - uses: actions/checkout@v4

azure-pipelines/build.yml

@@ -44,7 +44,7 @@ jobs:
 - job: macOS
   condition: ${{ parameters.includeMacOS }}
   pool:
-    vmImage: macOS-12
+    vmImage: macOS-14
   steps:
   - checkout: self
     fetchDepth: 0 # avoid shallow clone so nbgv can do its work.