servo: mark broken on darwin

= note: Undefined symbols for architecture arm64:
            "typeinfo for js::BaseProxyHandler", referenced from:
                typeinfo for ForwardingProxyHandler in libmozjs_sys-aaa8b4d8213d86fd.rlib(702045c0c9daef17-jsglue.o)
            "typeinfo for js::Wrapper", referenced from:
                typeinfo for WrapperProxyHandler in libmozjs_sys-aaa8b4d8213d86fd.rlib(702045c0c9daef17-jsglue.o)
          ld: symbol(s) not found for architecture arm64
          clang: error: linker command failed with exit code 1 (use -v to see invocation)

pkgs/by-name/se/servo/package.nix

@@ -180,6 +180,8 @@ rustPlatform.buildRustPackage {
   };
 
   meta = {
+    # undefined libmozjs_sys symbols during linking
+    broken = stdenv.hostPlatform.isDarwin;
     description = "Embeddable, independent, memory-safe, modular, parallel web rendering engine";
     homepage = "https://servo.org";
     license = lib.licenses.mpl20;