1. postproc now looks for postprocess.h (there is no postproc.h header).
2. pkg-config fallback condition now works (find_path/library set the
variable to ${var}-NOTFOUND but it was checking for an empty string).
This new module should be able to handle both libraries in the regular
paths and fallback to pkg-config.
It is also able to find dynamic libraries, not just static libraries.
It will generate imported targets with the name FFmpeg::<lib> that you
can use in your scripts.
The way it’s used in our main build script has been updated to match.
We also won’t link external libraries used by ffmpeg automatically since
it is not reliable and depend on custom options.
You should use a proper static build with no external dependencies or
a shared build that will have the proper dependencies listed.
