CI: macos-11 is no more; keep -12 and add -14

.github/workflows/main.yml

@@ -16,7 +16,7 @@ jobs:
     strategy:
       matrix:
         # Build each combination of OS and release/debug variants
-        os: [ "ubuntu-latest", "ubuntu-20.04", "macos-11", "macos-12" ]
+        os: [ "ubuntu-latest", "ubuntu-20.04", "macos-12", "macos-14" ]
         build-type: [ Release, Debug ]
         # Extra cmake flags.  GitHub Actions matrix overloads `include` to mean
         # 'add extra things to a job' and 'add jobs'.  You can add extra things
@@ -36,15 +36,19 @@ jobs:
             dependencies: "sudo apt install ninja-build"
           - os: "ubuntu-latest" # 22.04 at time of writing
             dependencies: "sudo apt install ninja-build"
-          - os: "macos-11"
+          - os: "macos-12"
             # The homebrew packages are broken at the moment and error out
             # after trying to install Python as a dependency of ninja because
             # 2to3 exists.  As a quick hack, delete it first.  This should be
             # removed once the homebrew install is fixed.
             dependencies: "rm -f /usr/local/bin/2to3 ; brew update && brew install ninja"
           - os: "macos-12"
+            variant: "C++17"
             dependencies: "rm -f /usr/local/bin/2to3 ; brew update && brew install ninja"
-          - os: "macos-12"
+            cmake-flags: "-DSNMALLOC_USE_CXX17=ON"
+          - os: "macos-14"
+            dependencies: "rm -f /usr/local/bin/2to3 ; brew update && brew install ninja"
+          - os: "macos-14"
             variant: "C++17"
             dependencies: "rm -f /usr/local/bin/2to3 ; brew update && brew install ninja"
             cmake-flags: "-DSNMALLOC_USE_CXX17=ON"