In Qt 6, we removed the "old" Harfbuzz and Harfbuzz-NG became the
only option. But the QT_HARFBUZZ=old environment variable would
still be read and would disable certain parts of the code path.
This has caused some confusion when porting older applications,
where QT_HARFBUZZ=old was used to work around issues with the
earlier versions of Harfbuzz-NG. Setting it now causes text to
disappear completely.
To avoid this confusion, we remove traces of the QT_HARFBUZZ
environment variable as well.
[ChangeLog][Text] Fixed an issue where setting the legacy
environment variable QT_HARFBUZZ=old would cause text to
disappear from the application.
Fixes: QTBUG-102774
Change-Id: I0f07cdb2418202fc36b82e766ad9547c34477175
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
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