qt6: widgets fixes — replace QDesktopWidget, use QGuiApplication::primaryScreen; switch dialog button map to QMultiMap; fix QFlags init and layout API; QtConcurrent lambda wrappers

build/CMakeFiles/d/ce39b0a4051ad0803bf91106ab4265342b199dd247f1327bf3702d63793dc4d6.d

@@ -6,6 +6,7 @@ Z/src/nglwidgets/nglwidgets_autogen/timestamp: \
   /opt/Qt/6.8.3/gcc_64/include/QtCore/QIODevice \
   /opt/Qt/6.8.3/gcc_64/include/QtCore/QList \
   /opt/Qt/6.8.3/gcc_64/include/QtCore/QMap \
+  /opt/Qt/6.8.3/gcc_64/include/QtCore/QMultiMap \
   /opt/Qt/6.8.3/gcc_64/include/QtCore/QPointF \
   /opt/Qt/6.8.3/gcc_64/include/QtCore/QPointer \
   /opt/Qt/6.8.3/gcc_64/include/QtCore/QProcess \
@@ -244,6 +245,7 @@ Z/src/nglwidgets/nglwidgets_autogen/timestamp: \
   /repo/Z/src/nglwidgets/nglwidgets_export.h \
   Z/src/nglwidgets/nglwidgets_autogen/moc_predefs.h \
   /repo/cmake/FindPopplerQt5.cmake \
+  /repo/include/poppler/qt5/poppler-qt5.h \
   /usr/bin/cmake \
   /usr/include/alloca.h \
   /usr/include/asm-generic/errno-base.h \