I am forking this off from #2022 because that thread got rather involved. I think the summary is:

1. stack exec -- exeName +RTS ... works fine to pass RTS options because -- causes further RTS arguments to not be processed.

2. stack exec exeName -- +RTS .. doesn't work because the -- is also visible to the exeName process.

One option for resolving this would be to deprecate the stack exec exeName -- ARGS form, perhaps even the stack exec exeName form. How can we deprecate it though? That would require adding stuff to stdout or stderr.

Either way, we should re-enable -rtsopts for stack, may as well have them if they are being parsed out of the commandline. Either way, we should thoroughly document using RTS options with exec.