qt6-webengine-docs is using an old version of CMake and fails to build

[opendragon (Norman Jaffe)]

qt6-webengine-docs has an internal copy of CMake that is version 3.12.2 (qt-cmake-private) while the CMake configuration files use features that appeared in CMake version 3.15 and the current version of CMake is >3.24.

Steps:

1. sudo port clean --all qt6-qtwebengine-docs
2. sudo port -v -c -s -f -N install qt6-qtwebengine-docs

The build fails:

--->  Computing dependencies for qt6-qtwebengine-docs.
--->  Fetching distfiles for qt6-qtwebengine-docs
--->  qtwebengine-everywhere-src-6.4.3.tar.xz does not exist in /opt/local/var/macports/distfiles/qt6
--->  Attempting to fetch qtwebengine-everywhere-src-6.4.3.tar.xz from https://distfiles.macports.org/qt6
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  420M  100  420M    0     0  75.2M      0  0:00:05  0:00:05 --:--:-- 73.1M
--->  Verifying checksums for qt6-qtwebengine-docs
--->  Checksumming qtwebengine-everywhere-src-6.4.3.tar.xz
--->  Extracting qt6-qtwebengine-docs
--->  Extracting qtwebengine-everywhere-src-6.4.3.tar.xz
Executing:  cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_aqua_qt6/qt6-qtwebengine-docs/work" && /opt/local/bin/xz -dc '/opt/local/var/macports/distfiles/qt6/qtwebengine-everywhere-src-6.4.3.tar.xz' | /usr/bin/tar -xf - 
--->  Configuring qt6-qtwebengine-docs
Executing:  cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_aqua_qt6/qt6-qtwebengine-docs/work/build" && /opt/local/libexec/qt6/bin/qt-configure-module /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_aqua_qt6/qt6-qtwebengine-docs/work/qtwebengine-everywhere-src-6.4.3 -webengine-icu -webengine-ffmpeg -webengine-native-spellchecker -verbose -- -DCMAKE_C_COMPILER=/usr/bin/clang -DCMAKE_CXX_COMPILER=/usr/bin/clang++ -DCMAKE_OBJC_COMPILER=/usr/bin/clang -DCMAKE_OBJCXX_COMPILER=/usr/bin/clang++ -DCMAKE_OSX_DEPLOYMENT_TARGET=12.0 -DCMAKE_INSTALL_NAME_DIR=/opt/local/libexec/qt6/lib 
CMake Error at /opt/local/libexec/qt6/lib/cmake/Qt6/QtProcessConfigureArgs.cmake:79 (list):
  list does not recognize sub-command POP_FRONT


Command failed:  cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_aqua_qt6/qt6-qtwebengine-docs/work/build" && /opt/local/libexec/qt6/bin/qt-configure-module /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_aqua_qt6/qt6-qtwebengine-docs/work/qtwebengine-everywhere-src-6.4.3 -webengine-icu -webengine-ffmpeg -webengine-native-spellchecker -verbose -- -DCMAKE_C_COMPILER=/usr/bin/clang -DCMAKE_CXX_COMPILER=/usr/bin/clang++ -DCMAKE_OBJC_COMPILER=/usr/bin/clang -DCMAKE_OBJCXX_COMPILER=/usr/bin/clang++ -DCMAKE_OSX_DEPLOYMENT_TARGET=12.0 -DCMAKE_INSTALL_NAME_DIR=/opt/local/libexec/qt6/lib 
Exit code: 1
Error: Failed to configure qt6-qtwebengine-docs: configure failure: command execution failed
Error: See /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_aqua_qt6/qt6-qtwebengine-docs/main.log for details.
Error: Follow https://guide.macports.org/#project.tickets if you believe there is a bug.
Error: Processing of port qt6-qtwebengine-docs failed

The shell script '/opt/local/libexec/qt6/bin/qt-configure-module' invokes 'qt-cmake-private' in the same directory, and that is just too old to work.

In the same directory is 'qt-cmake', which is version 3.24.4; note that this failure to build occurs with many of the qt6 ports, not just this one. In particular, all the '-docs' ports fail, except for qt6-qtbase-docs.