scripts: ext-toolchain: add option to overwrite config

It can be useful to overwrite an already generated config.
Option are simply added at the end of the config and make defconfig
will overwrite the relevant option with the new one.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
(cherry picked from commit f4dd18ca39)

scripts/ext-toolchain.sh

@@ -50,6 +50,7 @@ BIN_SPECS="
 	gdbserver: gdbserver
 "
 
+OVERWRITE_CONFIG=""
 
 test_c() {
 	cat <<-EOT | "${CC:-false}" $CFLAGS -o /dev/null -x c - 2>/dev/null
@@ -320,9 +321,13 @@ print_config() {
 	fi
 
 	# bail out if there is a .config already
-	if [ -f "${0%/scripts/*}/.config" ]; then
+	if [ -f "$config" ]; then
+		if [ "$OVERWRITE_CONFIG" == "" ]; then
 			echo "There already is a .config file, refusing to overwrite!" >&2
 			return 1
+		else
+			echo "There already is a .config file, trying to overwrite!"
+		fi
 	fi
 
 	case "$mktarget" in */*)
@@ -330,8 +335,11 @@ print_config() {
 		mktarget="${mktarget%/*}"
 	;; esac
 
+	if [ ! -f "$config" ]; then
+		touch "$config"
+	fi
 
-	echo "CONFIG_TARGET_${mktarget}=y" > "$config"
+	echo "CONFIG_TARGET_${mktarget}=y" >> "$config"
 
 	if [ -n "$mksubtarget" ]; then
 		echo "CONFIG_TARGET_${mktarget}_${mksubtarget}=y" >> "$config"
@@ -532,6 +540,10 @@ while [ -n "$1" ]; do
 			exit $?
 		;;
 
+		--overwrite-config)
+			OVERWRITE_CONFIG=y
+		;;
+
 		--config)
 			if probe_cc; then
 				print_config "$1"
@@ -573,6 +585,8 @@ while [ -n "$1" ]; do
 			echo -e "  is used to specify C flags to be passed to the "     >&2
 			echo -e "  cross compiler when performing tests."               >&2
 			echo -e "  This parameter may be repeated multiple times."      >&2
+			echo -e "  Use --overwrite-config before --config to overwrite" >&2
+			echo -e "  an already present config with the required changes.">&2
 			exit 1
 		;;