Add GitHub Actions CI: build on macOS 15 (M1)

- Installs Metal Toolchain
- Builds release binary
- Uploads compiled arm64 binary as artifact

Author: simba

.github/workflows/build.yml

@@ -0,0 +1,34 @@
+name: Build
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  build:
+    runs-on: macos-15
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Metal Toolchain
+        run: xcodebuild -downloadComponent MetalToolchain || true
+
+      - name: Resolve dependencies
+        run: swift package resolve
+
+      - name: Build (Release)
+        run: swift build -c release
+
+      - name: Verify binary
+        run: |
+          ls -lh .build/release/mlx-server
+          file .build/release/mlx-server
+
+      - name: Upload binary
+        uses: actions/upload-artifact@v4
+        with:
+          name: mlx-server-arm64
+          path: .build/release/mlx-server
+          retention-days: 30