kconfig: fix ncurses headers location

On some distors (eg. latesst openSuSE), the ncurses headers are not
located in the usual location.

Hard-code this location in the kconfig Makefile, as a (temporary?)
workaround.

Reported-by: Simon Gornall <sgornall@apple.com>
[Fix suggested by Simon]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

 # Default test suite configuration

 # Default DejaGnu configuration

 DG_TOOLNAME = gcc

 DG_TARGET_HOSTNAME = 127.0.0.1

 DG_TARGET_USERNAME = root

 # Default tests

 DG_C_TESTS = 

 DG_CPP_TESTS =