The production build takes too long

[gkpty]

Describe the bug
Every time i build for production it takes a really long time because everything is getting built again..

I want to only rebuild the files that have actually been modified since the last build.

possible solution
create a file called builds.json with the following structure:

{
   dirName:{
       fileName:{
          last_update:"",
          last_build:""
       },
       ...
   }
   ...
}

whenever the build command gets run,
it should first, for each file in the project, check for its last update using fs.statSync.mtime and update the last_update attribute for the file in the builds.json. Then if the file's last_update > last_build it will get added to an array called filesToBuild.

In the start command only the files in the filesToBuild Array should be built.