scripts/mkimage.sh: switch from abuild-apk to apk

The issue is that 'abuild-apk' creates root-owned files in the workdir,
and they cannot be removed later without root privileges.

'abuild-apk' is called only with 2 commands (add --initdb, update),
and in the context of the script they don't seem to be requiring
root privileges, so I'm proposing to substitute the calls with 'apk'.
This will automatically resolve the issue mentioned above.

Signed-off-by: Stanislav Kholmanskikh <stanislav.kholmanskikh@bell-sw.com>

scripts/mkimage.sh

@@ -297,7 +297,7 @@ for ARCH in $req_arch; do
 		# create root for caching packages
 		mkdir -p "$APKROOT/etc/apk/cache"
 		cp -Pr /etc/apk/keys "$APKROOT/etc/apk/"
-		abuild-apk --arch "$ARCH" --root "$APKROOT" add --initdb
+		apk --arch "$ARCH" --root "$APKROOT" add --initdb
 
 		if [ -z "$REPOS" ]; then
 			warning "no repository set"
@@ -307,7 +307,7 @@ for ARCH in $req_arch; do
 			echo "$repo" >> "$APKROOT/etc/apk/repositories"
 		done
 	fi
-	abuild-apk update --root "$APKROOT"
+	apk update --root "$APKROOT"
 
 	if [ "$_yaml" = "yes" ]; then
 		_yaml_out=${OUTDIR:-.}/latest-releases.yaml