kconfig/lxdialog: get ncurses CFLAGS with pkg-config

This makes "make menuconfig" also work on systems where ncurses is not
installed in a standard location (such as on NixOS).

This patch changes ccflags() so that it tries pkg-config first, and only
if pkg-config fails does it go back to the fallback/manual checks. This
is the same algorithm that ldflags() already uses.

Signed-off-by: Bjørn Forsman <bjorn.forsman@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>

scripts/kconfig/lxdialog/check-lxdialog.sh

@@ -21,7 +21,11 @@ ldflags()
 # Where is ncurses.h?
 ccflags()
 {
-	if [ -f /usr/include/ncursesw/curses.h ]; then
+	if pkg-config --cflags ncursesw 2>/dev/null; then
+		echo '-DCURSES_LOC="<ncurses.h>" -DNCURSES_WIDECHAR=1'
+	elif pkg-config --cflags ncurses 2>/dev/null; then
+		echo '-DCURSES_LOC="<ncurses.h>"'
+	elif [ -f /usr/include/ncursesw/curses.h ]; then
 		echo '-I/usr/include/ncursesw -DCURSES_LOC="<curses.h>"'
 		echo ' -DNCURSES_WIDECHAR=1'
 	elif [ -f /usr/include/ncurses/ncurses.h ]; then