For platforms not providing mkdtemp(), QTemporaryDir relied on an implementation
of q_mkdtemp() operating on char *, converting back and forth using
QFile::encodeName()/decodeName() when passing the name to QFileSystemEngine.
This caused failures on Windows (which uses "System"/Latin1 encoding)
for names containing characters outside the Latin1 space.
Reimplement q_mkdtemp() to operate on QString, which avoids the conversions
altogether and also enables the use of larger character spaces for the
pattern.
Add tests.
Task-number: QTBUG-54810
Change-Id: Ie4323ad73b5beb8a1b8ab81425f73d03c626d58a
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
c14c149b51