Integration test `3229-exe-targets` not up to date

[mpilgrem]

See:

• Add Backpack support to Stack #6865 (comment)
• stack build copies unnecessary executables when asked to build just a single executable #3486
• Fix #5974 If new Cabal copy is available, use it #6451

The test assumes that Stack builds all executables of a package once. That is no longet the case with, say, GHC 9.10.3.