Bug#893072: kexec-tools: use autotools-dev to update config.{sub,guess}

[YunQiang Su]

Package: src:kexec-tools
Version: 1:2.0.16-1
Control: blocks 893071

To build packages on some new ports, we need to update the config.{guess,sub}
files.

autotools-dev packages provides a way to archive this.

-- 
YunQiang Su