[MacPorts] #61868: libusb @1.0.24: cannot parse USB.h with mainline gcc versions due to variant pragma handling not accepted by gcc

[MacPorts]

#61868: libusb @1.0.24: cannot parse USB.h with mainline gcc versions due to
variant pragma handling not accepted by gcc
-----------------------------------+-----------------------
  Reporter:  dgonyier              |      Owner:  michaelld
      Type:  defect                |     Status:  reopened
  Priority:  Normal                |  Milestone:
 Component:  ports                 |    Version:  2.6.4
Resolution:                        |   Keywords:
      Port:  libusb, libusb-devel  |
-----------------------------------+-----------------------

Comment (by michaelld):

 Looks like this issue is present in USB.h through macOS 10.14 ... it does
 not seem to be present in 10.15 or 11.* ... actual testing on 10.14 shows
 build failures using gcc9 and gcc10 ... my my my! So, the trigger should
 be if the C compiler matches "gcc*" then force the LegacySupport", which
 would install and do a "fixincludes" on USB.h ... that should do the
 trick!

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Ticket URL: <https://trac.macports.org/ticket/61868#comment:22>
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