The special handling of ":/etc/localtime" should only apply if that's
the exact value of $TZ; the old code would have treated
"/etc/localtime" the same, due to stripping a leading ':' before
checking for it. We can also test whether to do that stripping using
startsWith().
When reading the content of files, avoid QTextStream's trip via
QString and back to QByteArray by using the QFile's readLine()
directly, or by using readAll().
Task-number: QTBUG-75585
Change-Id: I1524529a2c34d83a9fbd00d41c11f2d994dfc49d
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
333d7e6de4