[MacPorts] #71013: qt6: Update to future 6.8.0 to support macOS 15.

[MacPorts]

#71013: qt6: Update to future 6.8.0 to support macOS 15.
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  Reporter:  cgilles  |      Owner:  MarcusCalhoun-Lopez
      Type:  update   |     Status:  assigned
  Priority:  Normal   |  Milestone:
 Component:  ports    |    Version:
Resolution:           |   Keywords:  sequoia
      Port:  qt6      |
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Comment (by reneeotten):

 Replying to [comment:3 cgilles]:
 > What's doesn't works with QtWebEngine exactly?

 I can dig up a failed {{{main.log}}} at some point...

 > Anyway, you need 4Gb of RAM by core to compile QtWebEngine, else the
 linking will fail. So one core 4Gb, 2 cores 8Gb, etc... Here on my Macbook
 pro M1 16Gb, i created a VM Linux arm64 with 11 Gb and i compile
 QtWebEngine on 2 cores. It takes 8 hours to complete.

 Yeah, that's one of the issues... it takes forever to try and build it
 just to find out it fails at some point :( Time is limited and the
 upstream bug reports and/or commits to the {{{qtwebengine}}} repository
 don't see to cover the issue from a cursory look.

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Ticket URL: <https://trac.macports.org/ticket/71013#comment:4>
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