Fix CI: manual git checkout for legacy Swift, move 5.3 to legacy, remove macOS 14

Co-authored-by: mxcl <58962+mxcl@users.noreply.github.com>

Author: Copilot

.github/workflows/ci.yml

@@ -17,12 +17,9 @@ jobs:
     - run: git diff --exit-code
 
   apple:
-    runs-on: ${{ matrix.os }}
+    runs-on: macos-13
     strategy:
       matrix:
-        os:
-          - macos-13
-          - macos-14
         platform:
           - iOS
           - tvOS
@@ -42,7 +39,6 @@ jobs:
     strategy:
       matrix:
         swift:
-        - swift:5.3
         - swift:5.4
         - swift:5.5
         - swift:5.6
@@ -98,11 +94,23 @@ jobs:
         - swift:5.0
         - swift:5.1
         - swift:5.2
+        - swift:5.3
     container:
       image: ${{ matrix.swift }}
     steps:
-    - uses: actions/checkout@v3
-      # Using v3 instead of v4 because v4 requires node20 which needs glibc 2.28+
+    - name: Checkout code
+      run: |
+        apt-get update && apt-get install -y git
+        git clone --depth 1 --branch ${GITHUB_HEAD_REF:-${GITHUB_REF#refs/heads/}} https://github.com/$GITHUB_REPOSITORY .git-tmp || \
+        git clone --depth 1 https://github.com/$GITHUB_REPOSITORY .git-tmp
+        cd .git-tmp
+        git fetch origin $GITHUB_SHA
+        git checkout $GITHUB_SHA
+        cd ..
+        mv .git-tmp/* .
+        mv .git-tmp/.git .
+        rm -rf .git-tmp
+      # Manual checkout because actions/checkout@v3 and v4 both require node20 with glibc 2.28+
       # These old Swift containers (Ubuntu 18.04) only have glibc 2.27
 
     - run: useradd -ms /bin/bash mxcl