Update ci.yml

add 3.7.1 and 3.5.8 should use macos-12

Author: dalehenrich

.github/workflows/ci.yml

@@ -13,13 +13,14 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ ubuntu-20.04 ]
-        smalltalk: [ GemStone64-3.7.0, GemStone64-3.6.8, GemStone64-3.5.8 ]
-        include: 
-          - smalltalk: GemStone64-3.6.8
-            os: macos-latest
+        os: [ ubuntu-20.04, macos-latest ]
+        smalltalk: [ GemStone64-3.7.1, GemStone64-3.6.8, GemStone64-3.5.8 ]
+        exclude: 
           - smalltalk: GemStone64-3.5.8
             os: macos-latest
+        include: 
+          - smalltalk: GemStone64-3.5.8
+            os: macos-12
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v2