PyQt’s configure.py allows you to pass name=value or name+=value pairs as
command line arguments, and they will be written into generated .pro files.
However PyQtWebEngine (and I believe also QScintilla and other modules using
the same boilerplate) does not accept such pairs, which makes it inconvenient
for us in Debian (my use case is passing QMAKE_CXXFLAGS and QMAKE_LFLAGS).
It would be nice if you added such support. A very basic patch is attached.