By default, linting is not part of the build pipeline.
During build, the lint task is only used for checking linting issues. it will not re-write the components with the auto fix option.
In case you want to use the auto fix option for your components, you should use the bit lint --fix command on your workspace.
To add your lint task to your build pipeline you need to add its task into the build pipeline using the getBuildPipe of your env:
(built in envs come with an API to add new tasks to their existing pipe)
getBuildPipe(modifiers: GetBuildPipeModifiers = {}): BuildTask[] { return [...someTasks, linterTask]; }
To implement your own linter, see here.