[MacPorts] #56322: rust @1.26.0: buid failed on OS X <= 10.9

[MacPorts]

#56322: rust @1.26.0: buid failed on OS X <= 10.9
---------------------+----------------------
  Reporter:  l2dy    |      Owner:  g5pw
      Type:  defect  |     Status:  assigned
  Priority:  Normal  |  Milestone:
 Component:  ports   |    Version:
Resolution:          |   Keywords:
      Port:  rust    |
---------------------+----------------------

Comment (by kencu):

 OK - that did it:
 {{{
 $ port -v installed rust
 The following ports are currently installed:
   rust @1.26.0_0 (active) platform='darwin 13' archs='x86_64'
 date='2018-05-17T17:41:46-0700'
 }}}

 just blacklist clang and all the macports-clang versions below some
 critical cutoff.

 I don't know where it is that they started defaulting to `-integrated-as`
 -- clang-5.0 works, and I'd just go with that, unless somebody wants to
 spend the time to figure it out exactly.

-- 
Ticket URL: <https://trac.macports.org/ticket/56322#comment:18>
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