Merge pull request #1235 from mxcl/ci/mxcl/xcodebuild/swift

[ci] use Swift rather than Xcode versions

Author: mxcl

Diff for: .github/workflows/ci.yml

@@ -52,9 +52,9 @@ jobs:
           - tvOS
           - iOS
           - watchOS
-        xcode:
-          - ~12.4
-          - ^12.5
+        swift:
+          - 5.3
+          - 5.4
     steps:
     - uses: actions/checkout@v2
     - run: |
@@ -64,9 +64,9 @@ jobs:
       if: ${{ matrix.platform == 'macOS' }}
     - uses: mxcl/xcodebuild@v1
       with:
-        xcode: ${{ matrix.xcode }}
+        swift: ${{ matrix.swift }}
         platform: ${{ matrix.platform }}
         code-coverage: true
         warnings-as-errors: true
-      continue-on-error: ${{ matrix.xcode == '^12.5' }}
+      continue-on-error: ${{ matrix.swift == '5.4' }}
     - uses: codecov/codecov-action@v1