Making the web component package an easily deployable set of limited components from the developed resources for easy migration and browser support is the primary goal of build pipeline tools such as Grunt, Gulp, RequireJS, and webpack. During development, we could add a number of additional resources and write the Sass/LeSS content as such.
However, during the application serving phase, wherein the application is run on browser we would want to deliver the content in browser-understandable format. This needs a bit of compilation, a packaging task is involved. The build pipeline addresses such processes seamlessly for diverse frontend technologies used to develop our application.
Please note that either of these tools can help you build and serve your application. You can choose one based on your project needs and prior knowledge.