Need help for PPA repo, can pkg-config .pc files contain a relative path?

Hi, first of all I need to explain why I’m writing this.

I’m not very experienced with this, but I basically want to make a PPA repository on launchpad with ffmpeg compiled with NVENC support, since is the only way to have OBS recording with nvenc support enabled and I would like to make it easier for my friend who are not very experienced in compiling linux apps just adding my ppa then updating.

I obviously managed to compile it by myself on my system, but since afaik PPA work by compiling on launchpad, in those systems the NVENC headers are not present in the repository.
PS: I’m using apt-get source ffmpeg then debuild
In my system I just installed the nvenc headers in /usr/include and the pkg-config file in /usr/lib/pkgconfig/
But I’m clueless on how to solve this issue on launchpad, obviously it failed to build complaining about ffnvenc headers missing.

So I expect the only way is to accomplish this task is to include the ffnvenc headers + pkg-config file in the source code, I tried checking the configure script but honestly it’s too much for me tbh, it’s very long and complicated for me to understand but I came to the conclusion it necessarily needs a pkg-config .pc file for ffnvenc because does some sort of force-checking, and even if I manage to put relative headers files in the source code without using pkg-config, it complains about it missing (as I said it checks for the pkg-config file necessarily, hope you get me on what I tried here…

So after forcing the PKG_CONFIG_PATH variable with a relative path on the source code, I encountered some issues with the ffnvcodec.pc pkg-config script, since it still doesn’t find the headers.
It’s basically made in this way, it checks for the prefix where the include folder is, and by default is prefix=/usr and obviously it’s wrong.
Of course I need to point it to my source code, but it doesn’t seem to accept relative paths

For the record, everything works fine as I intended if I put an absolute path on the pkg-config .pc file like /home/me/ffmpegbuilddir/nvenc-headers/ but obviously I don’t know the absolute path on the launchpad build system.

So my question is: can pkg-config .pc files contain a relative path to my source code? I think it couldn’t be done otherwise rather than digging in the 73k lines configure script and get it working in another way