Add an "After Build" step where scripts can execute after building but before invoking

[stwr667]

Is your feature request related to a problem? Please describe.
I'm regularly running into issues where the output of the sam build step in the .aws-sam/build folder is missing an artifact, or has one that I want slightly modified when using the AWS Toolkit before the sam local invoke command immediately executes, but there's no way to do this. I'm currently resorting to filesystem watchers which is a real hack.

Describe the solution you'd like
Ideally, somewhere in the AWS Lambda config here:

there would be way to add a script that can be run to run any custom code after sam build but before sam local invoke.

Describe alternatives you've considered
I've tried:

• Just changing our build scripts, or the files under the project directory, but they all affect production behaviour. I need this to be executed only when running AWS Toolkit for debugging.
• Using filesystem watchers that perform behaviour when files are added to the .aws-sam/build folder which is a real hack.