mac: Remove unsupported option to flock

flock is not native on mac os. There is a package that can be installed,
https://github.com/discoteq/flock, but it does not support the -x
option. See https://github.com/discoteq/flock/issues/9

By default, flock is exclusive so there's no need for the -x in the
first place

Tested:
Verified no error with flock when running script on mac os

Change-Id: Iab6bdb2a378cace290ad61569ae40c86baebc264
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
1 file changed