autossh: fix manual set of ssh path

autossh: fix manual set of ssh path

The configure script that is bundled with autossh does not generate the
correct code for the AC_ARG_WITH() macro of --with-ssh. As a result, the
configure scripts always check the host location, and fails with ssh is
not found.

Restore the autoreconf that has been removed in the last bump to fix the
--with-ssh configure option.

Fixes:
http://autobuild.buildroot.net/results/25d/25d681f9df22c07cdf5a6b8756bfc2d5ecf36247/
http://autobuild.buildroot.net/results/f0a/f0ae62d0ed6bac011c507cfea7cd7157671baf39/
http://autobuild.buildroot.net/results/b15/b1546bb3e861c14771bdd03cda9ce2e9176a2069/

Cc: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>