abuild: fix -openrc to work with multiple subpackages

allow a single APKBUILD have multiple -openrc subpackages.

abuild.in

@@ -1788,7 +1788,7 @@ libs() {
 default_openrc() {
 	depends="$depends_openrc"
 	pkgdesc="$pkgdesc (OpenRC init scripts)"
-	install_if="openrc $pkgname=$pkgver-r$pkgrel"
+	install_if="openrc ${subpkgname%-openrc}=$pkgver-r$pkgrel"
 	local dir file
 	for dir in conf.d init.d; do
 		if [ -d "$pkgdir/etc/$dir" ]; then