QDirIterator: don't require NFD normalization on Darwin for validity

HFS+ filesystems do enforce NFD normalization, so the test worked for
those filesystems. But on APFS, the filesystem is normalization-
insensitive but preserves it, so our transformation caused valid files
to be rejected.

This commit also optimizes the solution for all systems too. Instead of
converting from 8-bit to UTF-16 then back to 8-bit (allocating memory in
both steps), we only convert to UTF-16. And if we detect the locale is
UTF-8, then we use the further optimized QUtf8::isValidUtf8 function
that doesn't allocate any memory at all (ditto for US-ASCII, the case of
someone running with LANG=C).

Fixes: QTBUG-76522
Change-Id: Ief874765cd7b43798de3fffd15aa0d81620ad317
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

0 files changed, 0 insertions, 0 deletions