How to use the minimist.sourcemaps function in minimist

'use strict';

var gulp = require('gulp');
var browserify = require('browserify');
var uglify = require('gulp-uglify');
var source = require('vinyl-source-stream');
var buffer = require('vinyl-buffer');
var rename = require('gulp-rename');
var gulpif = require('gulp-if');
var sass = require('gulp-sass');
var pug = require('gulp-pug');
var copy = require('gulp-copy');
var eslint = require('gulp-eslint');
var sourcemaps = require('gulp-sourcemaps');
var header = require('gulp-header');
var isSourcemaps = require('minimist')(process.argv.slice(2)).sourcemaps;
var appVersion = require('./package.json').version;


// LIB
gulp.task('lint', function() {
	return gulp.src('./lib/*.js').pipe(eslint())
		.pipe(eslint.format())
		// Brick on failure to be super strict
		.pipe(eslint.failOnError());
});

gulp.task('build', gulp.series('lint',function() {
	return browserify({ entries: 'standalone.js', debug: isSourcemaps }).bundle()
		.pipe(source('./granim.js'))
		.pipe(buffer())
		.pipe(gulpif(!isSourcemaps, header('/*! Granim v' + appVersion + ' - https://sarcadass.github.io/granim.js */\n')))