github/workflows: use xcode 13.1 if xcode 13.0 is set

I find it both hilarious and sad that Github decided that defaulting
to XCode 13.0 was a good idea... At least they added 13.1 quickly.

Ref actions/runner-images#4180
Ref actions/runner-images#4300

.github/workflows/build.yml

@@ -53,6 +53,14 @@ jobs:
     steps:
       - uses: actions/checkout@v2
 
+      - name: Override Xcode 13.0 if it's around
+        run: |
+          XCODE_PATH="$(xcode-select -p)"
+          if [[ "${XCODE_PATH}" = "/Applications/Xcode_13.0.app" ]]; then
+            sudo xcode-select -s "/Applications/Xcode_13.1.app"
+            echo "Updated Xcode path ${XCODE_PATH} -> $(xcode-select -p)"
+          fi
+
       - name: Install dependencies
         run: |
           brew update