[MacPorts] #61921: qt5-qtwebengine @5.15.2: does not build on macOS 10.13 with Xcode 9

[MacPorts]

#61921: qt5-qtwebengine @5.15.2: does not build on macOS 10.13 with Xcode 9
------------------------+-----------------------------
 Reporter:  dliessi     |      Owner:  (none)
     Type:  defect      |     Status:  new
 Priority:  Normal      |  Milestone:
Component:  ports       |    Version:
 Keywords:  highsierra  |       Port:  qt5-qtwebengine
------------------------+-----------------------------
 macOS 10.13.6 17G14042\\
 Xcode 9.4.1 9F2000

 The port qt5-qtwebengine fails because nothing is built.
 The configure phase ends with the following warnings:

 {{{
 WARNING: QtWebEngine requires at least version 10.0.0, but using Xcode
 version 9.4.1.
 WARNING: QtPdf requires at least version 10.0.0, but using Xcode version
 9.4.1.
 WARNING: QtWebEngine will not be built.
 WARNING: QtPdf will not be built.
 }}}

 See the
 [https://build.macports.org/builders/ports-10.13_x86_64-builder/builds/98527/steps
 /install-port/logs/stdio full log].

 I tried patching the configure phase to allow Xcode 9.4.1, but the build
 phase failed because of a missing symbol
 (`_responsibility_spawnattrs_setdisclaim`; unfortunately I didn't take
 note of which file required it and I have already cleaned the build
 attempt), so I assume Xcode 10 is really required.

 The version of Xcode in the buildbot is indeed 9.4.1, and although Xcode
 10.0.0 should run on macOS 10.13 I seem to recall that it wasn't
 recommended to install it (probably because of the SDK version).
 Is it still true?

 Answering [https://lists.macports.org/pipermail/macports-
 users/2020-December/049231.html my message to the mailing list], Ken
 [https://lists.macports.org/pipermail/macports-
 users/2020-December/049232.html suggested] that the buildbot be updated to
 use Xcode 10 on 10.13 (that's why I'm adding Ryan in Cc).

 An alternative solution is to create a new set of `qt514` ports.

 Ken suggested also to try forcing macports-clang 9.0: I will try later and
 report.

-- 
Ticket URL: <https://trac.macports.org/ticket/61921>
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