package/luarocks: fix buildroot addon vs 3.3.x

package/luarocks: fix buildroot addon vs 3.3.x

an internal API change introduced by version 3.3.0 causes the following failure:
```
Error: LuaRocks 3.3.1 bug (please report at https://github.com/luarocks/luarocks/issues).
Arch.: linux-x86_64
.../user/build/qarm/host/share/lua/5.3/luarocks/queries.lua:55: assertion failed!
stack traceback:
	[C]: in function 'assert'
	.../user/build/qarm/host/share/lua/5.3/luarocks/queries.lua:55: in function 'luarocks.queries.new'
	...m/host/share/lua/5.3/luarocks/cmd/external/buildroot.lua:322: in function 'luarocks.cmd.external.buildroot.command'
	(...tail calls...)
	[C]: in function 'xpcall'
	/home/user/build/qarm/host/share/lua/5.3/luarocks/cmd.lua:620: in function 'luarocks.cmd.run_command'
	/home/user/build/qarm/host/bin/luarocks:38: in main chunk
	[C]: in ?
```

Signed-off-by: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>