abuild: verify names of subpackages

This is to avoid things like:
http://git.alpinelinux.org/cgit/aports/commit/?id=81c0a4bb37e709ebc5add8394331d28209a61b6f

abuild.in

@@ -110,6 +110,13 @@ sanitycheck() {
 	[ -z "$url" ] && die "Missing url in APKBUILD"
 	[ -z "$license" ] && die "Missing license in APKBULID"
 
+	# check so no package names starts with -
+	for i in $pkgname $subpackages; do
+		case $i in
+		-*) die "${i%:*} is not a valid package name";;
+		esac
+	done
+
 	# check if CARCH, CBUILD, CHOST and CTARGET is set
 	if [ -z "$CARCH" ]; then
 		case "$(uname -m)" in