recordBuildRunnerPid method
Implementation
Future<void> recordBuildRunnerPid(String rootPath, int pid) async {
final pidsFile = io.File(p.join(packageDir(rootPath), "build_runner.pids"));
await pidsFile.create(recursive: true);
final sink = pidsFile.openWrite(mode: .writeOnlyAppend);
sink.writeln(pid);
await sink.close();
}