Guard QQmldebuggingEnabled by an env var

Authored by davidedmundson on Jun 9 2020, 8:07 PM.

Description

Guard QQmldebuggingEnabled by an env var

I don't understand why QQmlDebuggingEnabler prints a warning, it's no
less secure until other command line args are passed.

However the warning is scary, so lets put a guard on it.

BUG: 422228