main/lua-optarg: install minimal rock_manifest

main/lua-optarg/APKBUILD

 # Maintainer: Natanael Copa <ncopa@alpinelinux.org>
 pkgname=lua-optarg
+_rockname=optarg
 pkgver=0.2
-pkgrel=0
+pkgrel=1
 pkgdesc="Simple command line option parser for Lua"
 url="https://github.com/ncopa/lua-optarg"
 arch="noarch"
@@ -24,9 +25,13 @@ _package() {
 	pkgdesc="$pkgdesc $lver"
 	depends="lua$lver"
 	install_if="$pkgname=$pkgver-r$pkgrel lua$lver"
+	local rockdir="$subpkgdir/usr/lib/luarocks/rocks-$lver/$_rockname/$pkgver-1"
 
 	install -Dm644 "$builddir"/optarg.lua \
 		"$subpkgdir"/usr/share/lua/$lver/optarg.lua
+
+	mkdir -p "$rockdir"
+	echo 'rock_manifest = {}' > "$rockdir"/rock_manifest
 }
 
 sha512sums="347d958020a3fbd7a0ba553eccc3ba54f0732636e6a880bd254065ae9634b6a9397b0e4f48a720a0597672da62652ec6998c455f2719622ae6e9c06896e5c573  lua-optarg-0.2.tar.gz"