[MacPorts] #70655: Qt6-qtbase, missing #include and an issue for (some) older systems

[MacPorts]

#70655: Qt6-qtbase, missing #include and an issue for (some) older systems
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  Reporter:  Gandoon     |      Owner:  MarcusCalhoun-Lopez
      Type:  defect      |     Status:  assigned
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:  2.10.1
Resolution:              |   Keywords:
      Port:  qt6-qtbase  |
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Comment (by Gandoon):

 Replying to [comment:3 reneeotten]:
 > You should not have been prompted to update Qt6 on macOS 10.15 as it’s
 not supported there - so no point sending this upstream…You instead should
 have stayed on 6.4.2 - at least that is how it was intended. So there is
 something not correct in the Qt6-related PortGroups and/or I made a
 mistake when doing the update; I’ll try to correct that.
 >
 > It appears to be tricky enough to get everything to build on upstream
 supported systems (likely related to SDK versions and such) and I don’t
 have the time/interest/capabilities to do the work to try and get it to
 work folr older OSes. Marcus has been doing a great job at that, but
 hasn’t been around much lately. So not sure of how much help I can be
 here… I am afraid that once you possibly fix this thing here it will break
 in other places and the patch-work will keep continuing.

 So far the only other package I noticed any issues with for now is
 `qt6-qtdeclarative`. I may return with suggestions for older system users
 if it can be easily patched, but after reading this comment, I may not put
 too much effort into it and just revert to `@6.4.2`. We shall see if I
 have the energy. So far the only issues I saw seems to have been calls to
 functions not available on older systems and Qt had already covered some
 of the unsupported older systems with fallbacks. I have come across these
 `available()` functions before, e.g. I believe it is in iTerm2.

 I do realise that some manual tweaking is sometimes needed if one wishes
 to remain on an older system. It ends up being almost like a hobby to keep
 the system running as well as possible ;)

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Ticket URL: <https://trac.macports.org/ticket/70655#comment:5>
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