Проблема с настройкой сборки проекта?

// Подключение пакетов

var gulp = require('gulp');
var browserSync = require('browser-sync').create();
var less = require('gulp-less');
var plumber = require('gulp-plumber');
var notify = require('gulp-notify');
var autoprefixer = require('gulp-autoprefixer');
var scss = require('gulp-sass');
var sourcemaps = require('gulp-sourcemaps');
var pug = require('gulp-pug');
var del = require('del');
var runSequence = require('run-sequence');




// Задачи для Gulp

// LESS --> CSS
gulp.task('less', function() {
    return gulp.src('./src/less/main.less')
        .pipe(plumber({
              errorHandler: function(err) {
                notify.onError({
                  title: "Ошибка в CSS",
                  message: "<%= error.message %>"
                })(err);
              }
            }))
        .pipe(sourcemaps.init())
    	.pipe(less())
        .pipe(autoprefixer({
            overrideBrowserslist:  ['last 3 versions'],
            cascade: false
        }))
        .pipe(sourcemaps.write())
    	.pipe(gulp.dest('./build/css/'))
    	.pipe(browserSync.stream());
});


// SASS/SCSS --> CSS
gulp.task('scss', function() {
    return gulp.src('./src/scss/main.scss')
        .pipe(plumber({
            errorHandler: function(err) {
            notify.onError({
                title: "Ошибка в CSS",
                message: "<%= error.message %>"
            })(err);
            }
        }))
        .pipe(sourcemaps.init())
        .pipe(scss())
        .pipe(autoprefixer({
            overrideBrowserslist:  ['last 3 versions'],
            cascade: false
        }))
        .pipe(sourcemaps.write())
        .pipe(gulp.dest('./build/css/'))
        .pipe(browserSync.stream());
});


// .pug --> .html
gulp.task('pug', function() {
    return gulp.src('./src/pug/pages/**/*.pug')

    .pipe(plumber({
        errorHandler: notify.onError(function(err){
            return {
                title: 'Pug',
                message: err.message
            }
        })     
    }))
    .pipe(pug({
        pretty: true
    }))
    .pipe(gulp.dest('./build'))
    .pipe(browserSync.stream());
});


// Копирование
gulp.task('copy:js', function() {
    return gulp.src('src/js/**/*.*')
        .pipe(gulp.dest('./build/js'))
        .pipe(browserSync.stream());
});

gulp.task('copy:libs', function() {
    return gulp.src('src/libs/**/*.*')
        .pipe(gulp.dest('./build/libs'))
        .pipe(browserSync.stream());
});

gulp.task('copy:img', function() {
    return gulp.src('src/img/**/*.*')
        .pipe(gulp.dest('./build/img'))
        .pipe(browserSync.stream());
});


// Clean folder "Build"
gulp.task('clean:build', function() {
    return del('./build');
});







// Static server (using LESS)
// gulp.task('server', gulp.series('less', function() {
//     browserSync.init({
//         server: {baseDir: "./src/"}
//     });
//     gulp.watch('src/**/*.html').on('change', browserSync.reload);
// 	gulp.watch('src/less/*.less', gulp.series('less'));
// 	gulp.watch('src/**/*.js').on('change', browserSync.reload);
// }));


// Static server (using SCSS)
gulp.task('server', function() {
    browserSync.init({
        server: {baseDir: "./build/"}
    });
   
    gulp.watch('src/pug/**/*.*', gulp.series('pug'));
   
    //gulp.watch('src/**/*.less', gulp.series('less'));
    gulp.watch('src/scss/*.scss', gulp.series('scss'));
    
    gulp.watch('src/**/*.js', gulp.series('copy:js')); 
    gulp.watch('src/libs/**/*.*', gulp.series('copy:libs')); 
    gulp.watch('src/img/**/*.*', gulp.series('copy:img'));     

});







// Default command - gulp to start project
gulp.task('default', gulp.series('server', function(callback){
    runSequence(
        'clean:build',
        ['scss', 'pug', 'copy:js', 'copy:libs', 'copy:img'],
        'server',
        callback
    )
}));