语法: lua_package_cpath <lua-style-cpath-str>
默认: The content of LUA_CPATH environment variable or Lua's compiled-in defaults.
环境: http
设置set_by_lua，content_by_lua 和 其他脚本对Lua C模块的查找路径。 cpath路径字符串是标准Luacpath路径格式，;; 可被用来代表原始cpath路径。
从v0.5.0rc29发行版开始，特殊符号$prefix 或 ${prefix}可用于搜索路径字符串中。server prefix的值，通常是由Nginx服务启动时的-p PATH命令行决定的。
English source:
syntax: lua_package_cpath <lua-style-cpath-str>
default: The content of LUA_CPATH environment variable or Lua's compiled-in defaults.
context: http
Sets the Lua C-module search path used by scripts specified by set_by_lua,
content_by_lua and others. The cpath string is in standard Lua cpath form, and ;;
can be used to stand for the original cpath.
As from the v0.5.0rc29 release, the special notation $prefix or ${prefix} can be used in the search path string to indicate the path of the server prefix usually determined by the -p PATH command-line option while starting the Nginx server.