Why does building opentelemetry-cpp-contrib/instrumentation/nginx requires NGINX_VERSION and downloading Nginx? Can I just specify Nginx source myself?

[gregory112]

It seems that to configure it it requires NGINX_VERSION to be supplied, which will download Nginx. I intent to build Nginx from source anyway to add other modules, which means I already have Nginx source downloaded. How can I configure it to use existing Nginx source?

Steps to reproduce
cmake -DNGINX_VERSION=1.26.0

What is the expected behavior?
Can point to existing Nginx source

What is the actual behavior?
It downloads Nginx source again