Support Retaining Artifacts Generated During Build

[hawkinsw]

Add the --keep-temp flag to the roc build command to allow users to keep the temporary directories generated during builds. Having such a feature will make it easier for users to inspect intermediate files generated in the process of building a roc program.

[hawkinsw]

First, thank you to everyone for the work that you have done on roc! I am new to the community, but really enjoying myself so far!

My goal in joining the community, besides learning/using roc, was to work on platform development. I quickly realized I wanted to see the intermediate artifacts generated by the roc compiler. So, I added this flag thinking that it might help a "future someone like me".

I realize that I have not followed the CONTRIBUTING/README.md guide for including exhaustive tests with my PR. However, I didn't want to spam you with a bunch of code if this feature was not something that interests the group.

If there is an interest in accepting this PR, I will absolutely add tests!

Again, I am so excited to be part of the community and hope that my first initial, timid effort at contribution is helpful!

[Anton-4]

Welcome @hawkinsw,
I like this feature, if you can add just one test that runs quickly that would be fine :)

[hawkinsw]

Welcome @hawkinsw, I like this feature, if you can add just one test that runs quickly that would be fine :)

Thank you for the positive feedback! I was so nervous -- I wanted to make a good first impression! I will absolutely add a test.

I may not be able to write it immediately, but I hope you don't interpret that as lack of interest! Just a busy few days with $DAYJOB. Thank you again for the response and for being so welcoming!

[Anton-4]

I may not be able to write it immediately

All good, take your time :)