can't build ghc with package depending on lang installed

When I try to build jhc with ghc and have wxhaskell
installed,
the build fails because although lang-1.0 is hidden somehow
it is exposed (by --make??) by being a dependency of the
wxcore package.

If I uninstall wxhaskell then there is no problem...
however
it is annoying having to uninstall and re-install pkgs
just to build
something.  The same problem occurs with hs-plugins
installed
(instead of wxhaskell) iirc.

Trac metadata

Trac field	Value
Version	6.4
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	ResolvedFixed
Component	Compiler
Test case
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