We prefer the shared cache path, because there is no reason to give up
benefitting from sharing the content between applications. If that path
is not QFileInfo().isWritable(), we fall back to the local cache path.
However, there are reportedly systems with security solutions such as
AppArmor where the writable check passes and yet attempting to create a
file still fails. Then there is no cache in effect, because nothing ever
gets written out.
Handle this better: if writing the file fails and we still use our first
choice, the global cache location, fall back to the secondary choice
(the app-local path) and try again.
Pick-to: 6.2 6.1 5.15
Fixes: QTBUG-96789
Change-Id: Ifea32e9af0cf85aa70f3069256ed3d6a7e2fbe90
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Dalton Durst <dalton@ubports.com>
Reviewed-by: Andy Nichols <andy.nichols@qt.io>
46e6a9a759