Add TARGET option to cabal check

[ffaf1]

Closes #6282

e.g. cabal check ~/my-projects/reactive-strawberry/

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Include the following checklist in your PR:

• Patches conform to the coding conventions.
• Any changes that could be relevant to users have been recorded in the changelog.
• The documentation has been updated, if necessary.
• Manual QA notes have been included.
• Tests have been added. (Ask for help if you don’t know how to write them! Ask for an exemption if tests are too complex for too little coverage!)

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QA Notes

1. cabal init foo
2. cabal check foo

• with old cabal, you will get a 'check' doesn't take any extra arguments error
• with new cabal you will get a list of warnings

[fendor]

LGTM

[mpickering]

I think it's pretty confusing that cabal check TARGET is a completely different target syntax to cabal build TARGET or any other notion of TARGET in cabal.

Shouldn't cabal check work like cabal build.. so cabal check all, will check all the packages in the project scope. cabal check foo will check the package foo etc.

[ffaf1]

It makes sense, let me see if it is feasible (as now cabal check knows nothing about cabal.project).