kconfig: factor out ncurses check in a shell script

Cleaning up the lxdialog Makefile by factoring out the
ncurses compatibility checks.
This made the checks much more obvious and easier to extend.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

scripts/kconfig/lxdialog/Makefile

-HOST_EXTRACFLAGS := -DLOCALE 
-ifeq ($(shell uname),SunOS)
-HOST_LOADLIBES   := -lcurses
-else
-HOST_LOADLIBES   := -lncurses
-endif
+# Makefile to build lxdialog package
+#
 
-ifeq (/usr/include/ncurses/ncurses.h, $(wildcard /usr/include/ncurses/ncurses.h))
-        HOST_EXTRACFLAGS += -I/usr/include/ncurses -DCURSES_LOC="<ncurses.h>"
-else
-ifeq (/usr/include/ncurses/curses.h, $(wildcard /usr/include/ncurses/curses.h))
-        HOST_EXTRACFLAGS += -I/usr/include/ncurses -DCURSES_LOC="<ncurses/curses.h>"
-else
-ifeq (/usr/include/ncurses.h, $(wildcard /usr/include/ncurses.h))
-        HOST_EXTRACFLAGS += -DCURSES_LOC="<ncurses.h>"
-else
-	HOST_EXTRACFLAGS += -DCURSES_LOC="<curses.h>"
-endif
-endif
-endif
+check-lxdialog   := $(srctree)/$(src)/check-lxdialog.sh
+HOST_EXTRACFLAGS := $(shell $(CONFIG_SHELL) $(check-lxdialog) -ccflags)
+HOST_LOADLIBES   := $(shell $(CONFIG_SHELL) $(check-lxdialog) -ldflags)
+ 
+HOST_EXTRACFLAGS += -DLOCALE 
+
+.PHONY: dochecklxdialog
+$(obj)/dochecklxdialog:
+	$(Q)$(CONFIG_SHELL) $(check-lxdialog) -check $(HOSTCC) $(HOST_LOADLIBES)
 
 hostprogs-y	:= lxdialog
-always		:= ncurses $(hostprogs-y)
+always		:= $(hostprogs-y) dochecklxdialog
 
 lxdialog-objs := checklist.o menubox.o textbox.o yesno.o inputbox.o \
 		 util.o lxdialog.o msgbox.o
-
-.PHONY: $(obj)/ncurses
-$(obj)/ncurses:
-	@echo "main() {}" > lxtemp.c
-	@if $(HOSTCC) lxtemp.c  $(HOST_LOADLIBES); then \
-		rm -f lxtemp.c a.out; \
-	else \
-		rm -f lxtemp.c; \
-		echo -e "\007" ;\
-		echo ">> Unable to find the Ncurses libraries." ;\
-		echo ">>" ;\
-		echo ">> You must install ncurses-devel in order" ;\
-		echo ">> to use 'make menuconfig'" ;\
-		echo ;\
-		exit 1 ;\
-	fi

scripts/kconfig/lxdialog/check-lxdialog.sh

+#!/bin/sh
+# Check ncurses compatibility
+
+# What library to link
+ldflags()
+{
+	if [ `uname` == SunOS ]; then
+		echo '-lcurses'
+	else
+		echo '-lncurses'
+	fi
+}
+
+# Where is ncurses.h?
+ccflags()
+{
+	if [ -f /usr/include/ncurses/ncurses.h ]; then
+		echo '-I/usr/include/ncurses -DCURSES_LOC="<ncurses.h>"'
+	elif [ -f /usr/include/ncurses/curses.h ]; then
+		echo '-I/usr/include/ncurses -DCURSES_LOC="<ncurses/curses.h>"'
+	elif [ -f /usr/include/ncurses.h ]; then
+		echo '-DCURSES_LOC="<ncurses.h>"'
+	else
+		echo '-DCURSES_LOC="<curses.h>"'
+	fi
+}
+
+compiler=""
+# Check if we can link to ncurses
+check() {
+	echo "main() {}" | $compiler -xc -
+	if [ $? != 0 ]; then
+		echo " *** Unable to find the ncurses libraries."          1>&2
+		echo " *** make menuconfig require the ncurses libraries"  1>&2
+		echo " *** "                                               1>&2
+		echo " *** Install ncurses (ncurses-devel) and try again"  1>&2
+		echo " *** "                                               1>&2
+		exit 1
+	fi
+}
+
+usage() {
+	printf "Usage: $0 [-check compiler options|-header|-library]\n"
+}
+
+if [ $# == 0 ]; then
+	usage
+	exit 1
+fi
+
+case "$1" in
+	"-check")
+		shift
+		compiler="$@"
+		check
+		;;
+	"-ccflags")
+		ccflags
+		;;
+	"-ldflags")
+		ldflags
+		;;
+	"*")
+		usage
+		exit 1
+		;;
+esac