libarchive: bump to version 3.1.2

Switch to proper upstream source.
And account for many auto dependencies that were missing.
Also fixes link issues:
http://autobuild.buildroot.net/results/774/7747a043123e958952a16e0c0db823296c4e0594/



Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>