bug#64979: ghc-exceptions broken on i686 leads to lots of broken packages

[Csepp]

This came to my attention when trying to reconfigure my netbook, which
uses earlyoom, which requires Pandoc to build its docs.

http://ci.guix.gnu.org/build/1610832/details
http://ci.guix.gnu.org/build/1610832/log/raw