语法: debug = ngx.config.debug
环境: set_by_lua, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua*, body_filter_by_lua*, log_by_lua*, ngx.timer., init_by_lua, init_worker_by_lua**
这个布尔值代表当前 Nginx 是否为调试版本，既，在编译时使用./configure的可选项--with-debug。
该 API 在 0.8.7 版本首次引入。
English source:
syntax: debug = ngx.config.debug
context: set_by_lua, rewrite_by_lua*, access_by_lua*, content_by_lua*, header_filter_by_lua*, body_filter_by_lua*, log_by_lua*, ngx.timer., init_by_lua, init_worker_by_lua**
This boolean field indicates whether the current Nginx is a debug build, i.e., being built by the ./configure option --with-debug.
This field was first introduced in the 0.8.7.