Support --fast flag in `stack run`

When developing, it's typical to build without optimizations (`stack build --fast `). `stack run` effectively collapses a `build`/`execute` step into one command, but if I have been developing with `stack build --fast`, `stack run` forces recompilation of the world. Additionally, subsequent `stack build --fast` calls force _another_ recompilation.

With large projects with multi-minute build times especially, this is unfortunate: Can `stack run` support non-optimized builds (with a `--fast` flag?) in order to re-use incremental artifacts from developing with `stack build --fast`?