[MacPorts] #58869: ispc @1.11.0: fatal error: 'type_traits' file not found

[MacPorts]

#58869: ispc @1.11.0: fatal error: 'type_traits' file not found
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  Reporter:  ryandesign  |      Owner:  tenomoto
      Type:  defect      |     Status:  assigned
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:
Resolution:              |   Keywords:
      Port:  ispc        |
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Comment (by tenomoto):

 I need to setup the old versions.

 It is strange that clang-8.0 behaves differently across OS versions.

 The build failure on a newer (10.13, 14) was due to a failure to force
 require_active_variants.
 Fixed in
 [changeset:5eb768a54de36485a3c04d0502247e04ba734bc4/macports-ports]

 See: #58868

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Ticket URL: <https://trac.macports.org/ticket/58869#comment:7>
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