export MATLAB_BIN path in the makefile.

[Iron-Stark]

No description provided.

[zoq]

I think it might be useful to check the output of which matlab first and warn the user if the path is empty, what do you think? The Matlab path might be different for other distributions; if we set the path it might be difficult to solve potential issues without any additional insight.

[rcurtin]

I agree with that---our benchmarking setup is not necessarily the same setup others will have, so just checking if matlab is on the path first is a good step, and if it is not there then we should issue a warning that says that MATLAB_BIN is not set.

(Also, shouldn't we call it MATLAB_PATH since it is just the path to the directory containing MATLAB instead of MATLAB_BIN?)