This is a gulp-clean-css & clean-css 3 example.
When built via gulp build it produces a minified file with correct output and references to images & fonts.
Note that all sources from /src directory are copied to /public directory, however clean-css operates on /src folder only, i.e.:
cleanCSS({ target: sourceDir, relativeTo: sourceDir })For more details see discussion at clean-css/clean-css#854