Fix webengine-v8-snapshot-support configure

It needs to be checked for all cross builds not just embedded builds,
it doesn't need to be checked for 64-bit archictures, and it is helpful
to list it in the overview even if we only act on it later.

Change-Id: I68c571480186bb9564cb564ca561dfd284f6e231
Reviewed-by: Michal Klocek <michal.klocek@qt.io>