Nginx mod_security needs apache headers to compile, after some discussion Thomas Deutschmann of www-servers/nginx, he suggest me to logged feature request for www-servers/apache team to provide minimal use flags which provide apache only header files.
Steps to Reproduce:
1. emerge www-servers/nginx with NGINX_MODULES_HTTP security
2. it will trying to install full pledge www-servers/apache
www-servers/nginx needs full fledge www-servers/apache install when using NGINX_MODULES_HTTP security use flag
www-servers/apache should provide minimal use flags which install all apache header files
It will be usefull for system in which space is really limited, pulling full pledge www-servers/apache for a single module in www-servers/nginx is also not 'neat' and 'tidy'.