function packfeIIFEes6(cb) {
    try {
        src(`${feModuleSrc}/uibuilder.module.mjs`)
            .pipe(gulpEsbuild({
                outfile: 'uibuilder.es6.min.js',
                bundle: true,
                format: 'iife',
                platform: 'browser',
                minify: true,
                sourcemap: true,
                target: [
                    'es2016',
                    // Start of 2019
                    // 'chrome72',
                    // 'safari12.1',
                    // 'firefox65',
                    // 'opera58',

                    // For private class fields:
                    // 'chrome74',   // Apr 23, 2019
                    // 'opera62',    // Jun 27, 2019
                    // 'edge79',     // Jan 15, 2020
                    // 'safari14.1', // Apr 26, 2021
                    // 'firefox90',  // Jul 13, 2021

                    // If we need top-level await
                    // 'chrome89',  // March 1, 2021
                    // 'edge89',
                    // 'opera75',   // Mar 24, 2021
                    // 'firefox89', // Jun 1, 2021
                    // 'safari15',  // Sep 20, 2021
                ],
            }))
            .pipe(greplace(/="(.*)-mod"/, '="$1-es6.min"'))
            .pipe(dest(feDestAlt))

        src(`${feModuleSrc}/uibuilder.module.mjs`)
            .pipe(gulpEsbuild({
                outfile: 'uibuilder.es6.js',
                bundle: true,
                format: 'iife',
                platform: 'browser',
                minify: false,
                sourcemap: false,
                target: [
                    'es2016',
                ],
            }))
            .pipe(greplace(/version = "(.*)-mod"/, 'version = "$1-es6"'))
            .pipe(dest(feDestAlt))

        // fs.copyFileSync(`${feModuleSrc}/uibuilder.module.mjs`, `${feDest}/uibuilder.esm.js`)
    } catch (e) {
        console.error('Could not pack uibuilder.module.mjs for es6', e)
    }
    cb()
}
Pack (Uglify) front-end IIFE ES6 task
@param {Function} cb Callback