Allow for environmental variables to be set (backward compatible) for
defining the source and build directories of tensorflow.
Allow configuration without setting enviornmental variables
by directly assigning cmake values for TensorFlow_SOURCE_DIR
and TensorFlow_BUILD_DIR during cmake invocation or from
a cmake GUI.
Allow for environmental variables to be set (backward compatible) for defining the source and build directories of tensorflow.
Allow configuration without setting enviornmental variables by directly assigning cmake values for TensorFlow_SOURCE_DIR and TensorFlow_BUILD_DIR during cmake invocation or from a cmake GUI.