Synchronous vs. Asynchronous tasks

gulpfile.js

/*
  There are three main tasks I want to run one after the other (synchronously).
  Some of these tasks are divided into smaller tasks which can be run concurrently.
  Based on the output of gulp, it seems that this isn't quite happening,
  though I may be misreading it.

  Output:
    [15:14:07] Using gulpfile ~\projects\colibri\common-client\gulpfile.js
    [15:14:07] Starting 'lint'...
    [15:14:07] Finished 'lint' after 18 ms
    [15:14:07] Starting 'clean-dist'...
    [15:14:07] Starting 'clean-demo'...
    [15:14:07] Starting 'build-bower'...
    [15:14:07] Starting 'build-common-js'...
    [15:14:07] Starting 'build-common-tpl'...
    [15:14:07] Finished 'clean-demo' after 82 ms
    [15:14:07] Finished 'clean-dist' after 88 ms
    [15:14:07] Starting 'clean'...
    [15:14:07] Finished 'clean' after 5.38 μs
    [15:14:08] Finished 'build-common-tpl' after 438 ms
    [15:14:14] Finished 'build-common-js' after 6.41 s
    [15:14:14] Finished 'build-bower' after 6.42 s
    [15:14:14] Starting 'build'...
    [15:14:14] Finished 'build' after 6.35 μs
    [15:14:14] Starting 'default'...
    [15:14:14] Finished 'default' after 9.78 μs

  It looks to me like the "build" subtasks are starting before "clean" is finished. How can I prevent this?
  Is my desired result even possible?
*/
var gulp = require('gulp'),
  concat = require('gulp-concat'),
  rename = require('gulp-rename'),
  uglify = require('gulp-uglify'),
  clean = require('gulp-clean'),
  html2js = require('gulp-html2js'),
  lint = require('gulp-jshint'),
  lintConfig = require('./jshint');

gulp.task('lint', function(cb) {
  gulp.src([
      'base/**/*.js',
      'services/**/*.js',
      'widgets/**/*.js'
    ])
    .pipe(lint(lintConfig))
    .pipe(lint.reporter('default'));
  cb();
});

gulp.task('clean-dist', function() {
  return gulp.src('dist', {read: false, force: true})
    .pipe(clean());
});

gulp.task('clean-demo', function() {
  return gulp.src('demo/scripts', { read: false, force: true})
    .pipe(clean());
});

gulp.task('clean', ['clean-dist', 'clean-demo'], function(cb) {
  cb();
});

gulp.task('build-bower', function() {
  return gulp.src([
      'bower_components/angular/angular.js',
      'bower_components/angular-cookies/angular-cookies.js',
      'bower_components/angular-resource/angular-resource.js',
      'bower_components/angular-ui-router/release/angular-ui-router.js',
      'bower_components/angular-bootstrap/ui-bootstrap.js',
      'bower_components/angular-bootstrap/ui-bootstrap-tpls.js',
      'bower_components/angular-local-storage/dist/angular-local-storage.js',
      'bower_components/angular-sanitize/angular-sanitize.js',
      'bower_components/lodash/lodash.js'
    ])
    .pipe(concat('bower.js'))
    .pipe(rename('bower.min.js'))
    .pipe(uglify())
    .pipe(gulp.dest('dist'))
    .pipe(gulp.dest('demo/scripts'));
});

gulp.task('build-common-js', function() {
  return gulp.src([
      'base/**/*.js',
      'services/**/*.js',
      'widgets/**/*.js',
      '!**/*.spec.js'
    ])
    .pipe(concat('common-client.js'))
    .pipe(gulp.dest('demo/scripts'))
    .pipe(rename('common-client.min.js'))
    .pipe(uglify())
    .pipe(gulp.dest('dist'));
});

gulp.task('build-common-tpl', function() {
  return gulp.src('widgets/**/*.html')
    .pipe(html2js('angular.js', {
      adapter: 'angular',
      base: 'templates',
      name: 'ColibriCommonClient'
    }))
    .pipe(rename('common-client-tpl.js'))
    .pipe(gulp.dest('demo/scripts'))
    .pipe(uglify())
    .pipe(rename('common-client-tpl.min.js'))
    .pipe(gulp.dest('dist'));
})

gulp.task('build', ['build-bower', 'build-common-js', 'build-common-tpl'], function(cb) {
  cb();
});

gulp.task('default', ['lint', 'clean', 'build']);