Make QtWebEngineProcess.exe print warning to stderr instead of Windows debugger

Background

QtWebEngineProcess.exe cannot be run from a network path. A warning is raised if it  is attempted: https://code.qt.io/cgit/qt/qtwebengine.git/tree/src/core/web_engine_library_info.cpp?h=5.15.2#n189

However, Windows does not print qCritical() messages to the command line; instead, a separate tool like the IDE or DebugView is needed to view such messages.

It is common for users to try to deploy apps on shared drives (e.g. see the long list of commercial tickets linked to QTBUG-84632 and its duplicates), and this issue is usually only encountered after development is complete. So it would be good to increase the visibility of this message to end-users.

Suggestion

Instead of qCritical(), print the message to QTextStream(stderr)