Helpful environment variables
Setting these variables is usually unnecessary.
It is usually enough to have the feature or
a related binary first in your path.
Feature Environment variable(s)
Compiler....CC, CXX, FC
CUDA........CUDA_TOOLKIT_ROOT_DIR, CUDA_BIN_PATH
OpenMM......OPENMM_PLUGIN_DIR, OPENMM_DIR, OPENMM_HOME
FFTW........FFTW_DIR, FFTW_HOME
MKL.........MKLROOT, MKL_HOME