[GHC] #12485: -package-db flags now need to be sorted by dependency order

[GHC]

#12485: -package-db flags now need to be sorted by dependency order
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        Reporter:  niteria           |                Owner:
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:  8.0.3
       Component:  Package system    |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  phab:D2613
       Wiki Page:                    |
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Comment (by ezyang):

 bgamari notes that the cabal08 test will need to be adjusted once we fix
 this properly. We dropped the test for GHC 8.0 since it wasn't really
 testing something meaningful.

 The Cabal change is here https://github.com/haskell/cabal/pull/4008 but
 Duncan objected to computing ABI hashes on every build, so the patch is in
 limbo right now.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12485#comment:36>
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