ERROR: libnpp not found while ./configure

[Roi Rodriguez]

Summary of the bug:
How to reproduce:

I'm trying to build ffmpeg from the last master branch version on an ubuntu desktop 20.04.04. Cuda libraries are installed. When i configure:

$ ./configure --enable-nonfree --enable-cuda-nvcc --enable-libnpp --extra-cflags=-I/usr/local/cuda/include --extra-ldflags=-L/usr/local/cuda/lib64

ERROR: libnpp not found

If you think configure made a mistake, make sure you are using the latest
version from Git.  If the latest version fails, report the problem to the
ffmpeg-user@ffmpeg.org mailing list or IRC #ffmpeg on irc.libera.chat.
Include the log file "ffbuild/config.log" produced by configure as this will help
solve the problem.

I'm attaching the mentioned ffbuild/config.log file. As you can see it says he cannot find npp.h, but npp.h is present in /usr/local/cuda/include, passed as extra cflags.