[GHC] #12499: Support multiple library import libs

[GHC]

#12499: Support multiple library import libs
-------------------------------------+-------------------------------------
           Reporter:  Phyx-          |             Owner:
               Type:  feature        |            Status:  new
  request                            |
           Priority:  normal         |         Milestone:  8.2.1
          Component:  Runtime        |           Version:  8.0.1
  System (Linker)                    |
           Keywords:                 |  Operating System:  Windows
       Architecture:                 |   Type of failure:  GHC rejects
  Unknown/Multiple                   |  valid program
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 Our implementation of import libraries only support single library import
 libs.

 These are by far the most common ones. However it is possible to make
 multi library import libraries.

 E.g. one import library pointing to multiple dlls. `binutils` correct
 supports these and with #5987 GHC will be relying on them to work.

 It makes sense that we are able to load them in GHCi as well. This will be
 required for a fully working dynamic GHC on Windows.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12499>
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