[MacPorts] #54363: ghc: needs a runtime dependency for it's build compiler

[MacPorts]

#54363: ghc: needs a runtime dependency for it's build compiler
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  Reporter:  mojca                   |      Owner:  neverpanic
      Type:  defect                  |     Status:  assigned
  Priority:  Normal                  |  Milestone:
 Component:  ports                   |    Version:
Resolution:                          |   Keywords:  lion
      Port:  ghc hs-bytestring-show  |
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Comment (by kencu):

 So, I can only see three ways through this ticket's issue.

 1. Whitelist a compiler for ghc, like clang-4.0, and always build it with
 that on all systems older than 10.10, say. Then add this as a runtime
 dependency as well. Easy, simple. This is what I would likely suggest.

 2. Check each build of ghc on the buildbots, and make a runtime dep on the
 compiler that built the binary if it's not a default compiler for that
 system. Also pretty easy. Wasteful if ghc is built on the system with a
 newer compiler (eg. clang-4.0 will build it on 10.6 setup with
 LibcxxOnOlderSystems, so there is no need to install clang-3.4 which might
 otherwise be the default that built the binary).

 3. Some kind of complicated portfile logic to pick an installed compiler,
 or install one, and reset the `clang-wrapper` during activation. Most
 elegant, maybe, but ++ work.

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Ticket URL: <https://trac.macports.org/ticket/54363#comment:13>
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