The current cuda package provides a /opt/cuda/lib64 symlink, but not /opt/cuda/lib. This causes problems with some build systems (e.g. cmake) not finding some libraries by default that are provided by the CUDA toolkit. For some reason cmake's find_package seems to look into $CUDA_PATH/lib/cmake by default, but not into $CUDA_PATH/lib64/cmake.

So I suggest to add this to the PKGBUILD:

ln -s lib64 "${_prepdir}/opt/cuda/lib"

The effect can be tested e.g. with cmake finding Thrust. Create this CMakeLists.txt:

cmake_minimum_required(VERSION 3.24)
project(test)
find_package(Thrust REQUIRED)

Then running "cmake ." in the directory containing this file should not result in any warning or error.