Bug#1061610: debhelper: cp --update=none requires coreutils 9.3 or newer

[Sven Joachim <svenjoac@gmx.de>]

Package: libdebhelper-perl
Version: 13.12
Severity: important
X-Debbugs-Cc: Sven Joachim <svenjoac@gmx.de>, debian-hurd@lists.debian.org

Commit 018a0c9a7164f ("Dh_Lib.pm: Fix warning from `cp -n`") uses cp's
--update=none option which has been introduced rather recently, namely
in coreutils 9.3.  Older versions of cp do not understand this option,
complain and refuse to operate.  For instance dh_update_autotools_config
fails with older coreutils:

,----
| $ cp --version | head -n1
| cp (GNU coreutils) 9.1
| $ dh_update_autotools_config
| cp: option '--update' doesn't allow an argument
| Try 'cp --help' for more information.
| dh_update_autotools_config: error: cp -a --update=none --reflink=auto config.guess debian/.debhelper/bucket/files/ec2577614252326f889df1de97b9a457c03a9a94811048563c211a44496d8ba3.tmp returned exit code 1
`----

This is obviously bad for backports, more urgently it is going to make
many packages FTBFS on hurd-i386 which is stuck at coreutils 9.1-1.

I will open a separate bug on coreutils for giving the questionable
advice to use the --update=none option.