Add Swift 6.0 CI for building carton for macOS (#483)

* add Swift 6 in CI with special hack

* revert meaningless indent diff

.github/workflows/swift.yml

@@ -14,6 +14,12 @@ jobs:
     strategy:
       matrix:
         include:
+          - os: macos-14
+            xcode: "15.4"
+            swift: "6.0"
+            swift-install:
+              dir: "swift-6.0-branch/xcode"
+              version: "swift-6.0-DEVELOPMENT-SNAPSHOT-2024-06-07-a"
           - os: macos-14
             xcode: "15.4"
             swift: "5.10"
@@ -28,6 +34,13 @@ jobs:
       - name: Select Xcode version
         run: sudo xcode-select --switch /Applications/Xcode_${{ matrix.xcode }}.app/Contents/Developer
 
+      - name: Install Swift ${{ matrix.swift }}
+        if: ${{ matrix.swift-install != null }}
+        run: bash ci/mac/install-swift.bash
+        env:
+          SWIFT_DIR: ${{ matrix.swift-install.dir }}
+          SWIFT_VERSION: ${{ matrix.swift-install.version }}
+
       - name: Check Swift version
         run: swift --version
 
@@ -55,7 +68,6 @@ jobs:
           - swift:
               dir: "swift-5.9.2-release/ubuntu2204"
               version: "swift-5.9.2-RELEASE"
-
     steps:
       - name: Checkout the repository
         uses: actions/checkout@v4

ci/mac/install-swift.bash

@@ -0,0 +1,25 @@
+#!/bin/bash
+set -ue
+cd "$(dirname "$0")/../.."
+
+mkdir -p install
+cd install
+
+set -x
+pwd
+curl -fLO https://download.swift.org/${SWIFT_DIR}/${SWIFT_VERSION}/${SWIFT_VERSION}-osx.pkg
+installer -target CurrentUserHomeDirectory -pkg ${SWIFT_VERSION}-osx.pkg
+
+toolchain=~/Library/Developer/Toolchains/${SWIFT_VERSION}.xctoolchain
+
+set +x
+swift_id=$(plutil -extract CFBundleIdentifier raw ${toolchain}/Info.plist)
+
+set -x
+echo "TOOLCHAINS=${swift_id}" >> $GITHUB_ENV
+
+# https://github.com/apple/swift/issues/73327#issuecomment-2120481479
+find ${toolchain}/usr/bin -type f | xargs -n 1 -I {} \
+  sudo codesign --force --preserve-metadata=identifier,entitlements --sign - {}
+
+echo "DYLD_LIBRARY_PATH=${toolchain}/usr/lib/swift/macosx" >> $GITHUB_ENV