Use AC_CANONICAL_TARGET instead of deprecated AC_CANONICAL_SYSTEM

m4/arch.m4

@@ -3,7 +3,7 @@
 # Use dpkg-architecture from the source tree to set sh_var using DEB_VAR for
 # the target architecture, to avoid duplicating its logic.
 AC_DEFUN([_DPKG_ARCHITECTURE], [
-AC_REQUIRE([AC_CANONICAL_SYSTEM])dnl
+AC_REQUIRE([AC_CANONICAL_TARGET])dnl
 $2=`cd $srcdir/scripts; \
     PERL5LIB=$(pwd) ./dpkg-architecture.pl -t$target -q$1 2>/dev/null`
 ])# _DPKG_ARCHITECURE