split out lint job

.github/workflows/pull_request.yml

@@ -6,40 +6,85 @@ permissions:
   contents: read
 
 jobs:
-  mac_build_and_test:
+  lint:
     if: github.repository == 'ml-explore/mlx-swift'
-    runs-on: [self-hosted, macos]
+    runs-on: ubuntu-latest
+    container:
+      image: swift:6.2-rhel-ubi9
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           submodules: recursive
-
-      - name: Verify MetalToolchain installed
-        shell: bash
-        run: xcodebuild -showComponent MetalToolchain
-
+
       - name: Setup uv
         uses: astral-sh/setup-uv@v6
         with:
-            python-version: ${{ inputs.python-version }}
             activate-environment: true
 
-      - name: Setup swift-format
+      - name: Setup pre-commit
         shell: sh
         run: |
           uv pip install pre-commit
-          brew install swift-format
+
+      - name: Clone swift-format
+        shell: sh
+        run: |
+          cd /tmp
+          LATEST_TAG=$(curl -s https://api.github.com/repos/swiftlang/swift-format/releases/latest | \
+            grep '"tag_name":' | \
+            sed -E 's/.*"([^"]+)".*/\1/')
+          echo "swift-format $LATEST_TAG"
+          git clone --branch $LATEST_TAG --depth 1 https://github.com/swiftlang/swift-format.git
+          echo "SWIFT_FORMAT_VERSION=$LATEST_TAG" >> $GITHUB_OUTPUT
+
+      - name: Cache swift-format build
+        uses: actions/cache@v4
+        id: cache-swift-format
+        with:
+          path: /tmp/swift-format/.build
+          key: ${{ runner.os }}-swift-format-build-${{ needs.lint.outputs.SWIFT_FORMAT_VERSION }}
+
+      - name: Build swift-format
+        if: steps.cache-swift-format.outputs.cache-hit != 'true'
+        shell: sh
+        run: |
+          cd /tmp/swift-format
+          swift build -c release
+
+      - name: Link swift-format to /usr/local/bin
+        shell: sh
+        run: |
+          cd /tmp/swift-format
+          ln -s "$(swift build --show-bin-path -c release)/swift-format" /usr/local/bin/swift-format
 
-      - name: Setup cmake
+      - name: Configure safe directory for git
         shell: sh
         run: |
-          brew install cmake ninja
+          git config --global --add safe.directory "$GITHUB_WORKSPACE"
 
       - name: Run style checks
         shell: sh
         run: |
           pre-commit run --all || (echo "Style checks failed, please install pre-commit and run pre-commit run --all and push the change"; echo ""; git --no-pager diff; exit 1)
+
+  mac_build_and_test:
+    needs: lint
+    if: github.repository == 'ml-explore/mlx-swift'
+    runs-on: [self-hosted, macos]
+    steps:
+      - uses: actions/checkout@v5
+        with:
+          submodules: recursive
+
+      - name: Verify MetalToolchain installed
+        shell: bash
+        run: xcodebuild -showComponent MetalToolchain
 
+      - name: Setup cmake
+        shell: sh
+        run: |
+          brew install cmake ninja
+
       - name: Build (Xcode, macOS)
         shell: sh
         run: |