The requirement to separate debug and release DLLs on Windows stems from
the Visual Studio C run-time library appearing in two different variants
(debug and release) and not mixing well. It's possible to perform builds
without optimzations and with debug symbols while linking against the
release version of the C run-time, but at the same time the debug
version of the run-time brings other developer visible advantages.

MinGW on the other hand does not have this distinction, does not ship
with separate DLLS and does also not require the VS C runtime library.
Therefore we do not need this separation for MinGW, which means that our
packages can be reduced in size and application developers wishing to
debug their applications do not have to use debug builds of the Qt
libraries or run into Qt internal debug code.

Task-number: QTBUG-78445
Change-Id: Idf588606091298dc44262c4c89e689df18d34747
Reviewed-by: Cristian Adam <cristian.adam@qt.io>
Reviewed-by: Jörg Bornemann <joerg.bornemann@qt.io>