Use separate CI matrices for the three supported platforms

.github/workflows/test.yml

@@ -12,21 +12,12 @@ on:
       - master
 
 jobs:
-  build:
-    runs-on: ${{ matrix.os }}
+  linux_x86:
+    runs-on: ubuntu-latest
     strategy:
       matrix:
-        os: [ubuntu-latest, macos-latest]
         emacs_version: [23.4, 24.1, 24.2, 24.3, 24.4, 24.5, 25.1, 25.2, 25.3, 26.1, 26.2, 26.3, 27.1, 27.2, 28.1, 28.2, 29.1, 29.2, 29.3, release-snapshot, snapshot]
-        exclude:
-          - os: macos-latest
-            emacs_version: 23.4
-          - os: macos-latest
-            emacs_version: 24.1
-          - os: macos-latest
-            emacs_version: 24.2
-
-    steps:
+    steps: &common_steps
     - uses: actions/checkout@v4
     - name: Setup Emacs
       uses: ./
@@ -36,3 +27,17 @@ jobs:
       run: emacs --version
     - name: Check nix tools visible
       run: "nix-shell -p cowsay --run 'cowsay hello'"
+  macos_x86:
+    runs-on: macos-11
+    strategy:
+      matrix:
+        emacs_version: [24.3, 24.4, 24.5, 25.1, 25.2, 25.3, 26.1, 26.2, 26.3, 27.1, 27.2, 28.1, 28.2, 29.1, 29.2, 29.3, release-snapshot, snapshot]
+    steps:
+      <<: *common_steps
+  macos_arm:
+    runs-on: macos-latest
+    strategy:
+      matrix:
+        emacs_version: [28.1, 28.2, 29.1, 29.2, 29.3, release-snapshot, snapshot]
+    steps:
+      <<: *common_steps