lua-rocks: Install configuration: "Debug"

[dedok]

OS:
Ubuntu 16.04

Reproduce:
Follow instruction from Readme

Output from luarocks:
[100%] Built target driver
[100%] Built target driver
Install the project...
-- Install configuration: "Debug"
-- Installing: /usr/local/lib/tarantool/pg/driver.so
-- Installing: /usr/local/share/tarantool/pg/init.lua
Updating manifest for /usr/local/lib/luarocks/rocks