lua-rocks: Force pkgsrc unzip.

Otherwise it complains:

Error: Failed unpacking rock file: /tmp/luarocks_luarocks-rock-digestif-0.3-1-B5qFAU/digestif-0.3-1.src.rock: 'unzip -n' program not found. Make sure unzip is installed and is available in your PATH (or you may want to edit the 'variables.UNZIP' value in file '/usr/pkg/etc/luarocks/config-5.4.lua')

devel/lua-rocks/Makefile

@@ -1,4 +1,4 @@
-# $NetBSD: Makefile,v 1.11 2020/07/02 10:26:18 nia Exp $
+# $NetBSD: Makefile,v 1.12 2020/07/02 12:13:36 nia Exp $
 
 DISTNAME=	luarocks-3.3.1
 PKGNAME=	${DISTNAME:S/luarocks/${LUA_PKGPREFIX}-rocks/}
@@ -19,6 +19,8 @@ MAKE_FILE=	GNUmakefile
 
 .include "../../mk/bsd.prefs.mk"
 
+PREFER.unzip=	pkgsrc
+
 HAS_CONFIGURE=	yes
 USE_LANGUAGES=	# none
 

devel/lua-rocks/distinfo

@@ -1,7 +1,8 @@
-$NetBSD: distinfo,v 1.6 2020/07/01 11:06:40 nia Exp $
+$NetBSD: distinfo,v 1.7 2020/07/02 12:13:36 nia Exp $
 
 SHA1 (luarocks-3.3.1.tar.gz) = b85a4afd890d172994f4ebc95fe647f71de7eeb4
 RMD160 (luarocks-3.3.1.tar.gz) = 937a2d6d62474e3245927dc77fbe982b8ca4f2bb
 SHA512 (luarocks-3.3.1.tar.gz) = 0a695ceb30ae575cbca52abd2aad9675e33a234c53c5d1e125442d874c21e0e3cf6157431f07085e4311f81833680366adfe5c626a66cb5880380b48899a116a
 Size (luarocks-3.3.1.tar.gz) = 241636 bytes
 SHA1 (patch-GNUmakefile) = 1f84ae6e926a57b07abcc65789d784c8e6a0fa75
+SHA1 (patch-src_luarocks_core_cfg.lua) = 24c8c7e66fa12b2daf67924ac8ae0a2458380250

devel/lua-rocks/patches/patch-src_luarocks_core_cfg.lua

@@ -0,0 +1,15 @@
+$NetBSD: patch-src_luarocks_core_cfg.lua,v 1.1 2020/07/02 12:13:36 nia Exp $
+
+It seems to not like NetBSD unzip(1).
+
+--- src/luarocks/core/cfg.lua.orig	2020-02-07 10:24:14.000000000 +0000
++++ src/luarocks/core/cfg.lua
+@@ -253,7 +253,7 @@ local function make_defaults(lua_version
+          MKTEMP = "mktemp",
+ 
+          ZIP = "zip",
+-         UNZIP = "unzip -n",
++         UNZIP = "@PREFIX@/bin/unzip -n",
+          GUNZIP = "gunzip",
+          BUNZIP2 = "bunzip2",
+          TAR = "tar",