On BSD systems (tested on macOS and FreeBSD), you *can* lseek(2) or
ftell(3) on a pipe and get its current position. But QFile will not get
the position when the file is sequential, so we need to return 0.
Technically speaking, we ought to do the same for block devices, but if
you're redirecting stdin, stdout or stderr in the unit test to or from a
block device, you deserve the extra work to add that yourself to the
test.
Change-Id: I3868166e5efc45538544fffd14d8a74e92963fe7
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@qt.io>
5d2240718c