[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 Edward Z. Yang <ezyang@…>):

 In [changeset:"ee4e1654c31b9c6f6ad9b19ece25f040bbbcbd72/ghc" ee4e165/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="ee4e1654c31b9c6f6ad9b19ece25f040bbbcbd72"
 Support for abi-depends for computing shadowing.

 Summary:
 This is a complete fix based off of
 ed7af26606b3a605a4511065ca1a43b1c0f3b51d for handling
 shadowing and out-of-order -package-db flags simultaneously.

 The general strategy is we first put all databases together,
 overriding packages as necessary.  Once this is done, we successfully
 prune out broken packages, including packages which depend on a package
 whose ABI differs from the ABI we need.

 Our check gracefully degrades in the absence of abi-depends, as
 we only check deps which are recorded in abi-depends.

 Contains time and Cabal submodule update.

 Signed-off-by: Edward Z. Yang <ezyang at cs.stanford.edu>

 Test Plan: validate

 Reviewers: niteria, austin, bgamari

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D2846

 GHC Trac Issues: #12485
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12485#comment:37>
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