This turned out to be a small error inside a CMake script which slipped into the OptiX SDK 7.5.0 release but can easily be resolved locally.
It’s going to be fixed in the upcoming OptiX SDK release.
Inside CMake/cuda/FindCUDA/run_nvcc.cmake
you replace these two lines:
function(cuda_execute_process status command)
...
endfunction()
with
macro(cuda_execute_process status command)
...
endmacro()