Ensure new health endpoint builds on MacOS (#1215)

* Add mac build to CI

* Always return an error for Health when not linux

* Change macos workflow

* Rename macos tests

* Disable health API test on Mac

Co-authored-by: Michael Sproul <michael@sigmaprime.io>

beacon_node/rest_api/tests/test.rs

@@ -1253,6 +1253,7 @@ mod validator_attestation {
     }
 }
 
+#[cfg(target_os = "linux")]
 #[test]
 fn get_health() {
     let mut env = build_env();