Also run CI on x86-64 macOS

Author: phil-opp

.github/workflows/build.yml

@@ -44,7 +44,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        platform: [ubuntu-latest, macos-latest, windows-latest]
+        platform: [ubuntu-latest, macos-12, macos-latest, windows-latest]
 
     runs-on: ${{ matrix.platform }}
     timeout-minutes: 15