[MacPorts] #55979: libmpdclient @2.14_0 fails to build on mavericks

[MacPorts]

#55979: libmpdclient @2.14_0 fails to build on mavericks
---------------------------+-----------------------
  Reporter:  tehcog        |      Owner:
      Type:  defect        |     Status:  new
  Priority:  Normal        |  Milestone:
 Component:  ports         |    Version:  2.4.2
Resolution:                |   Keywords:  mavericks
      Port:  libmpdclient  |
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Comment (by ryandesign):

 Replying to [comment:8 lbschenkel]:
 > Thanks Craig. Makes sense. The strange thing is that it works on my
 system and the build slaves.

 It will succeed for from-source builds, and fail for binary installs.

 > Anyway, I agree that `post-destroot` is more correct. I have made the
 change and tested it on my machine.

 Please do commit that.

 Please also use `system` instead of `exec`.

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Ticket URL: <https://trac.macports.org/ticket/55979#comment:9>
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