--exec --file-watch combo not working as expected

### Steps to reproduce

Choose a repo and run:

~~~
stack build --exec "echo run me, please!" --file-watch
~~~
The echo doesn't echo yet. Type 'help'. The executable then runs eg

~~~
stack build --exec "echo run me, please!" --file-watch

help
run me, please!

help: display this help
quit: exit
build: force a rebuild
watched: display watched files
ExitSuccess
Type help for available commands. Press enter to force a rebuild.
quit

~~~

Associated with this, build does not seem to force a build.

### Expected

I expected the executable to run initially,, before kicking the file-watch cycle in the guts.

### Actual

the --exec runs *after* typing help

### version

~~~
$ stack --version
Version 1.3.2 x86_64 hpack-0.15.0
~~~