Use Xcode 12.3 on CI

Author: MaxDesiatov

.github/workflows/main.yml

@@ -126,7 +126,7 @@ jobs:
             ${{ runner.os }}-sccache-v10-
       - name: Build macOS installable archive
         run: |
-          sudo xcode-select --switch /Applications/Xcode_12.2.app/Contents/Developer/
+          sudo xcode-select --switch /Applications/Xcode_12.3.app/Contents/Developer/
           xcodebuild -version
           ./utils/webassembly/ci.sh
         env: