code: function runGruntfile () {
          var path = require('path'),
              child = require('child_process');
  
          this.filesSrc.forEach(function (gruntfile) {
              grunt.log.writeln('Loading ' + gruntfile + '...');
  
              var cmd = process.execPath,
                  args = process.execArgv.concat(process.argv[1], ['--gruntfile', path.resolve(gruntfile)]);
  
              var result = child.spawnSync(cmd, args);
              if (result.error) {
                  grunt.log.error(result.stdout);
              } else {
                  grunt.log.ok(result.stdout);
              }
          })
      }
docs: sync spawn