Support lua/metrics for debian 10

[jmonterrubio]

Prerequisites

• [ X] Put an X between the brackets on this line if you have done all of the following:
  • Checked that your issue isn't already filled: https://github.com/issues?utf8=✓&q=is%3Aissue+user%3Aidealista
  • Checked that there is not already provided the described functionality

Description

Nginx make step fails with an error because of lua-nginx-module.
For v0.10.13 the error is:
error: cast between incompatible function types from 'size_t ()(ngx_http_lua_script_engine_t )' {aka 'long unsigned int ()(struct )'} to 'void ()(ngx_http_lua_script_engine_t )' {aka 'void ()(struct )'} [-Werror=cast-function-type]

For v0.10.15 the error is:
fatal error: luajit.h: No such file or directory

Steps to Reproduce

1. Use a debian 10 environment to install nginx
2. Enable metrics using nginx_prometheus_metrics_enabled: true
3. Include the lua nginx module:

---

nginx_external_modules:

• name: lua
  version: '0.10.13'
  url: https://github.com/openresty/lua-nginx-module/archive/v0.10.13.tar.gz

---

Versions

2.2.0