/usr/bin/ld: objs/addon/nginx-dav-ext-module-3.0.0/ngx_http_dav_ext_module.o:/root/nginx-dav-ext-module-3.0.0/ngx_http_dav_ext_module.c:186: multiple definition of `ngx_http_dav_ext_module'; objs/addon/nginx-dav-ext-module/ngx_http_dav_ext_module.o:/www/server/nginx/src/nginx-dav-ext-module/ngx_http_dav_ext_module.c:186: first defined here