var all = require('gulp-all')

var styl_dir = 'path/to/styles/dir'
var js_dir   = 'path/to/scripts/dir'

function build() {
    return all(
        gulp.src(styl_dir + '/**/*')
            // build Styles
            .pipe(gulp.dest('dist_dir')),
        gulp.src(js_dir + '/**/*')
            // build Scripts
            .pipe(gulp.dest('dist_dir'))
    )
}

gulp.task('build', build)

var scriptBundles = [/*...*/]

function build(){
    var subtasks = scriptBundles.map(function(bundle){
        return gulp.src(bundle.src).pipe(/* concat to bundle.target */)
    })
    return all(subtasks)
}