anchor.diff:  
   /// Whether to include "--warning=no-unknown-keyword" when invoking tar.
   ///
  -/// This flag quiets warnings that come from opening OS X-generated tarballs on
  -/// Linux, but only GNU tar >= 1.26 supports it.
  +/// BSD tar (the default on OS X) can insert strange headers to a tarfile that
  +/// GNU tar (the default on Linux) is unable to understand. This will cause GNU
  +/// tar to emit a number of harmless but scary-looking warnings which are
  +/// silenced by this flag.
   final bool _noUnknownKeyword = _computeNoUnknownKeyword();
   bool _computeNoUnknownKeyword() {
     if (!Platform.isLinux) return false;
  
positive.code:   }
  
    var args = [
      "--extract",
      "--gunzip",
      "--no-same-owner",
  
negative.code:   // system path. So, if executable looks like it needs that (i.e. it doesn't
    // have any path separators in it), then spawn it through a shell.
    if (Platform.isWindows && !executable.contains('\\')) {
      args = ["/c", executable, ...args];
      executable = "cmd";
    }
  
  