"make check" fails in fileutils-4.1 if SIMPLE_BACKUP_SUFFIX in env

Hi,

fileutils/fileutils-4.1/tests/cp/backup-is-src doesn't take account that the
user might have SIMPLE_BACKUP_SUFFIX in the environment: "make check" fails in
this case.

Because it's only the shell script's environment, I think it should be OK to
simply remove SIMPLE_BACKUP_SUFFIX, as in the attached patch.

It's not a simple job to replace ~ with a shell variable in this script because
of the <<\EOF

Cheers ... Duncan.

--- backup-is-src.bu	Sun Oct 22 07:45:33 2000
+++ backup-is-src	Tue Oct  8 14:07:13 2002
@@ -5,6 +5,8 @@
   cp --version
 fi
 
+[ -n "$SIMPLE_BACKUP_SUFFIX" ] && unset SIMPLE_BACKUP_SUFFIX
+
 framework_failure=0
 rm -f a a~ || framework_failure=1
 echo a > a || framework_failure=1