Add CI job for macos

.github/workflows/build_macos.yaml

@@ -0,0 +1,38 @@
+name: Build (macOS)
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+# Cancel already running jobs
+concurrency:
+  group: build_macos_${{ github.head_ref }}
+  cancel-in-progress: true
+
+env:
+  CARGO_TERM_COLOR: always
+  RUST_BACKTRACE: 1
+
+jobs:
+  build:
+    name: macos - build
+    runs-on: macos-latest
+    steps:
+      - uses: actions/checkout@v4
+        # We purposefully dont cache here as build_and_test will always be the bottleneck
+        # so we should leave the cache alone so build_and_test can make more use of it.
+      - name: Install cargo-hack
+        uses: taiki-e/install-action@v2
+        with:
+          tool: cargo-hack@0.6.16
+      - name: Install deps
+        run: brew install gcc
+      - name: Ensure that dev tools compiles and has no warnings with no features enabled
+        run: cargo clippy --locked --all-targets -- -D warnings
+      - name: Ensure that shotover-proxy compiles and has no warnings under every possible combination of features
+        # some things to explicitly point out:
+        # * clippy also reports rustc warnings and errors
+        # * clippy --all-targets is not run so we only build the shotover_proxy executable without the tests/benches
+        run: cargo hack --feature-powerset --at-least-one-of valkey,cassandra,kafka,opensearch --exclude-features kafka-cpp-driver-tests,cassandra-cpp-driver-tests clippy --locked --package shotover-proxy -- -D warnings