Note: Documentation fixes for https://docs.haskellstack.org/en/stable/ should target the "stable" branch, not master.

Please include the following checklist in your PR:

• Any changes that could be relevant to users have been recorded in the ChangeLog.md
• The documentation has been updated, if necessary.

I'm still testing this in a more complex use case. However, the simple test case I devised was:

• stack new foo

• Modify the Setup.hs file to add import Acme.Missiles

• Add acme-missiles-0.3 as an extra-dep

• Add the following custom-setup block to foo.cabal:

  custom-setup
    setup-depends: base >= 4.6,
                   Cabal >= 1.24 && < 1.25,
                   acme-missiles
  

• Set build-type to Custom

• Confirm that without the patch, the package refuses to compile. With the patch, it compiles just fine.

@borsboom Maybe we can sync up later on adding this as an integration test case?