version up : OpenBLAS 0.2.15. Add make-ext-options to specify more make options.
OpenBLAS 0.2.15 was released. It supports more recent platforms like Intel Boardwell and Skylake and it supports pure C implementation as well. So I introduced make-ext-options parameter so that we can easily specify more options.
I have not tried it at all, so can you please try this version on your project using OpenBLAS ?