util-linux: take ${sbindir} from the environment if it is set there

Signed-off-by: Phil Blundell <pb@pbcl.net>
Upstream-Status: Inappropriate [configuration]

--- util-linux-2.21.2/configure.ac~	2012-09-22 09:29:12.354215377 +0100
+++ util-linux-2.21.2/configure.ac	2012-09-22 16:47:14.713628946 +0100
@@ -67,7 +67,9 @@
 usrbin_execdir='${exec_prefix}/bin'
 AC_SUBST([usrbin_execdir])
 
-usrsbin_execdir='${exec_prefix}/sbin'
+if [ -z "$usrsbin_execdir" ]; then
+   usrsbin_execdir='${exec_prefix}/sbin'
+fi
 AC_SUBST([usrsbin_execdir])
 
 usrlib_execdir='${exec_prefix}/'$libdirname