Fixes Ticket4922.

Commit 06010238 broke configure, since
the inversion ! was missed while converting the grep to a case
statement.
Reviewed-by: Nicolas George <george@nsup.org>
Reviewed-by: Timothy Gu <timothygu99@gmail.com>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>