build-tool-depends in setup-depends

[nomeata]

While trying to use cabal to build a project that the author has setup with stack, I found myself wanting to add build-tool-depends to setup-depends:

custom-setup
  setup-depends:
      base
    , Cabal
    , containers
    , directory
    , filepath
    , genapply
    , process
  build-tool-depends:
    genapply:genapply

but Cabal seems to not know how to handle build-tool-depends in custom-setup. Is that intentional, or an oversight?

[hvr]

Duplicate of #4648

[23Skidoo]

Closing in favour of #4648.