debian: Regenerate config.guess using debhelper

debian: Regenerate config.guess using debhelper

This is a change introduced in 5.10.0-2ubuntu2 with the changelog:

> xfsprogs upstream has regressed config.guess, so use
> dh_update_autotools_config.

The 5.10.0 tarball has a config.guess that breaks builds on RISC-V:
...
UNAME_MACHINE = riscv64
UNAME_RELEASE = 5.0.0+
UNAME_SYSTEM  = Linux
UNAME_VERSION = #2 SMP Sat Mar 9 22:34:53 UTC 2019
configure: error: cannot guess build type; you must specify one
make[1]: *** [Makefile:131: include/builddefs] Error 1
...

Reported-by: Steve Langasek <steve.langasek@ubuntu.com>
Signed-off-by: Bastian Germann <bastiangermann@fishpost.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>