ファイル削除にはgulpプラグインを使わない ref: http://qiita.com/shinnn/items/bd7ad79526eff37cebd0

file0.txt

var rimraf = require('rimraf');

gulp.task('clean', function (cb) {
  rimraf('./dir', cb);
});

gulp.task('build', ['clean'], function() {
  // Something
});

file1.txt

// !!! DEPRECATED WAY !!!
gulp.task('clean', function() {
  return gulp.src('./dir', {read: false})
    .pipe(rimraf());
});

file2.txt

var del = require('del');

gulp.task('clean', function(cb) {
  del(['dist', 'tmp', '**/*.log'], cb);
});

gulp.task('build', ['clean'], function() {
  // Something
});

file3.txt

gulp.task('clean', del.bind(null, ['.tmp', 'dist']));

file4.txt

// !!! DEPRECATED WAY !!!
gulp.task('clean', function(cb) {
  gulp.src(['dist', 'tmp', '**/*.log'], {read: false})
    .pipe(rimraf());
});