[MacPorts] #55005: GMP fails to build on Sierra with Xcode 9.0

[MacPorts]

#55005: GMP fails to build on Sierra with Xcode 9.0
--------------------------+---------------------------------
  Reporter:  lucaspettey  |      Owner:  MarcusCalhoun-Lopez
      Type:  defect       |     Status:  closed
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:  2.4.1
Resolution:  invalid      |   Keywords:
      Port:  gmp          |
--------------------------+---------------------------------
Changes (by mf2k):

 * status:  assigned => closed
 * resolution:   => invalid


Comment:

 It builds fine on the [http://packages.macports.org/gmp/ buildbot].

 You have not installed/updated the command line tools for Xcode 9 in High
 Sierra.

 {{{
 :info:configure configure: error: C++ compiler not available, see
 config.log for details
 }}}

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Ticket URL: <https://trac.macports.org/ticket/55005#comment:3>
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