[MacPorts] #70278: chez-scheme fails on 10.10 and earlier

[MacPorts]

#70278: chez-scheme fails on 10.10 and earlier
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  Reporter:              |      Owner:  mohd-akram
  barracuda156           |
      Type:  defect      |     Status:  assigned
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:  2.9.3
Resolution:              |   Keywords:  yosemite, mavericks, mountainlion,
      Port:  chez-       |  lion, snowleopard
  scheme                 |
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Comment (by ryandesign):

 In #60698 we worked around the problem by blacklisting `{clang < 800}`. It
 would be better if chez-scheme would only use `__builtin_add_overflow` if
 the compiler supports it. At present, they use it if
 `USE_OVERFLOW_INTRINSICS` is defined, and they define it for gcc 5 or
 greater or any version of clang, which is clearly wrong. I filed a bug
 report with them here: https://github.com/cisco/ChezScheme/issues/845

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Ticket URL: <https://trac.macports.org/ticket/70278#comment:2>
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