cuDNN: Help dependents find libs/includes on Power arch (#16128)
cuDNN: Help dependents find libs/includes on Power arch (#16128)

On Power architectures cuDNN will install in a target directory. This
sets cuDNN_ROOT to point to the subdirectory to help dependents use
this install.
LLNL/spack,LLNL/spack,LLNL/spack,iulian787/spack,LLNL/spack,iulian787/spack,iulian787/spack,iulian787/spack,iulian787/spack,LLNL/spack