Use Link Time Optimization (LTO) during compilation

[vincejv]

Default/stock nginx used in several distros has this compiler flag enabled for best performance.
Example output from Ubuntu

nginx version: nginx/1.18.0 (Ubuntu)
built with OpenSSL 3.0.2 15 Mar 2022
TLS SNI support enabled
configure arguments: --with-cc-opt='-g -O2 -ffile-prefix-map=/build/nginx-dSlJVq/nginx-1.18.0=. -flto=auto 
-ffat-lto-objects -flto=auto -ffat-lto-objects -fstack-protector-strong -Wformat -Werror=format-security -fPIC 
-Wdate-time -D_FORTIFY_SOURCE=2' --with-ld-opt='-Wl,-Bsymbolic-functions -flto=auto -ffat-lto-objects -flto=auto 
-Wl,-z,relro -Wl,-z,now -fPIC' --prefix=/usr/share/nginx --conf-path=/etc/nginx/nginx.conf 
--http-log-path=/var/log/nginx/access.log --error-log-path=/var/log/nginx/error.log 
--lock-path=/var/lock/nginx.lock --pid-path=/run/nginx.pid --modules-path=/usr/lib/nginx/modules 
--http-client-body-temp-path=/var/lib/nginx/body
--http-fastcgi-temp-path=/var/lib/nginx/fastcgi --http-proxy-temp-path=/var/lib/nginx/proxy 
--http-scgi-temp-path=/var/lib/nginx/scgi --http-uwsgi-temp-path=/var/lib/nginx/uwsgi
--with-compat --with-debug --with-pcre-jit --with-http_ssl_module
--with-http_stub_status_module --with-http_realip_module --with-http_auth_request_module
--with-http_v2_module --with-http_dav_module
--with-http_slice_module --with-threads
--add-dynamic-module=/build/nginx-dSlJVq/nginx-1.18.0/debian/modules/http-geoip2
--with-http_addition_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_sub_module

• https://gcc.gnu.org/wiki/LinkTimeOptimization