maintainer: am-ft: add option to cater to clock skews

maintainer: am-ft: add option to cater to clock skews

* maintainer/am-ft: Add option '-S', giving a number of seconds to sleep
after copying the tarball to the remote system and before unpacking,
building and testing it.  This is to cater to situations where the clock
of the remote system is skewed (in the past) w.r.t. the clock the local
system the tarball has been built on.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>