dune exec -- foo on Windows needs to consider dune exec -- foo.exe when working out if there is a program to (re)compile. At the moment, the behaviour is mixed:

• if _build/install/default/bin/foo.exe has previously been built, then you get a potentially stale execution of foo if its sources have changed
• if _build/install/default/bin/foo.exe hasn't previously been built, then you get an error.

Specifying dune exec -- foo.exe works consistently, but this has two problems:

• It's surprising on Windows (unless the user has done something really weird with the PATHEXT environment variable)
• It's not good for a cross-platform set-up since dune exec -- foo.exe will fail on a (Unix) system which installs foo.exe as foo with the executable bit set.

(Dune 2.4.0; Windows mingw32; OCaml 4.08.1)