Fix tst_QDateTime::systemTimeZoneChange() for 32-bit systems

The test verified that a LocalTime's time since Epoch changes when the
system time-zone changes. This works when the QDateTime object is in
short form and recomputes its offset from UTC every time it is needed,
but fails with a pimpled QDateTime, as this caches its offset from UTC
when it is created, saving the recomputation which - in the far more
usual case where the system time-zone does not change in the lifetime
of a QDateTime object - would normally produce the same result.

Changed the test to use a newly-created QDateTime constructed with the
same parameters, which doesn't have the cached out-of-date knowledge
of its zone offset. Removed the XFAIL. Made the test data-driven and
added test-cases: one so close to the Epoch that it should be short
even on 32-bit systems, one so far that it's pimpled even on 64-bit
systems (used in reproducing the issue in order to debug it).

This then revealed that Android 5 doesn't seem to support the POSIX
zone IDs used by this test, so it now verifies that LocalTime has the
expected offset from UTC after zone changes, QSKIP()ping if not.

Documented that the behavior of LocalTime is undefined after a change
to the system time-zone. Cleaned up the existing doc of Qt::TimeSpec
in the process.

Fixes: QTBUG-89889
Change-Id: I1058f47a1ff3ee1c326f3579ac80bd8bab242e28
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit 02ae1b522193b60e7a5c8e5eff7a15d25b0f7aae)

0 files changed, 0 insertions, 0 deletions