This is very confusing as seen in #12974 or #12906. My suggestion would be "legacy."
.on("end", function () {
            console.log(
              "Result diff can be found at " + BUILD_DIR + MOZCENTRAL_DIFF_FILE
            );
            done();
          });
      });
  })
);
gulp.task("externaltest", function (done) {
  console.log();
  console.log("### Running test-fixtures.js");
  safeSpawnSync("node", ["external/builder/test-fixtures.js"], {
    stdio: "inherit",
  });
  console.log();
  console.log("### Running test-fixtures_esprima.js");
  safeSpawnSync("node", ["external/builder/test-fixtures_esprima.js"], {
    stdio: "inherit",
  });
  done();
});
gulp.task(
  "npm-test",
  gulp.series(
    gulp.parallel("lint", "externaltest", "unittestcli", "typestest"),
    "lint-chromium"
  )
);