dialog: force linking with ncurses

Otherwise the build breaks with:
configure: error: no curses library found

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/dialog/dialog.mk

@@ -6,7 +6,7 @@
 DIALOG_VERSION:=1.1-20100428
 DIALOG_SOURCE:=dialog-$(DIALOG_VERSION).tgz
 DIALOG_SITE:=ftp://invisible-island.net/dialog
-
+DIALOG_CONF_OPT = --with-ncurses
 DIALOG_DEPENDENCIES = ncurses
 
 define DIALOG_INSTALL_TARGET_CMDS