Build on macos13 Intel and macos-14 ARM

macos-latest is macOS 12 Intel currently. Per [the post announcing macOS 14 runner availability][macos14ann], `macos-latest` will skip macos-13 and move to macos-14 by June 2024. Per the [M1 runner announcement][m1ann], only the macos-14 runners will have ARM and will have it by default, so we'll use that to get macOS ARM testing.

[macos14ann]: https://github.blog/changelog/2024-01-30-github-actions-macos-14-sonoma-is-now-available/
[m1ann]: https://github.blog/changelog/2024-01-30-github-actions-introducing-the-new-m1-macos-runner-available-to-open-source/

.github/workflows/makefile.yml

@@ -10,7 +10,10 @@ jobs:
   build:
     strategy:
       matrix:
-        os: [ubuntu-latest, macOS-latest]
+        os:
+          - ubuntu-latest
+          - macos-13
+          - macos-14
     runs-on: ${{ matrix.os }}
 
     steps: