Use gcc@11 for macos-10.15

Author: JorikSchellekens

.github/workflows/build.yml

@@ -73,6 +73,10 @@ jobs:
       - name: Install dependencies
         run: brew install cmake boost icu4c
 
+      - name: Install gcc (macos 10)
+        run: brew install gcc@11
+        if: matrix.os == 'macos-10.15'
+
       - name: Build kudu
         run: |
           sh build.sh