Add a flag to avoid generation of .hi, .o, .dyn_* files
When running tests involving GHC (eg. when developing GHC plugins), it is cumbersome and frustrating to have to constantly clean up the .hi, .o, and .dyn_* files that GHC leaves behind. There should be a way to tell GHC not to generate these files at all, or if they're really needed during the build process, to clean them up on its own once it's finished with them.
(Apologies if this is a duplicate issue -- "hi" and "o" are difficult terms to search on the bug tracker.)