debian: Fix cross build.

Cross-building openvswitch with debuild -aARCH (or equivalent) fails
because the target architecture is not getting passed to configure.
Thus binaries like ovs-appctl get built using the build host
architecture.

Signed-off-by: Ed Swierk <eswierk@skyportsystems.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>

debian/rules

@@ -45,7 +45,7 @@ configure-stamp:
 	cd _debian && ( \
 		test -e Makefile || \
 		../configure --prefix=/usr --localstatedir=/var --enable-ssl \
-			--sysconfdir=/etc CFLAGS="$(CFLAGS)" \
+			--sysconfdir=/etc --host=$(DEB_HOST_GNU_TYPE) CFLAGS="$(CFLAGS)" \
 			$(buildflags) $(DATAPATH_CONFIGURE_OPTS))
 	touch configure-stamp