Use MKL BinaryBuilder Julia package by default

[amartinhuertas]

No description provided.

[hammy4815]

This would be really convenient - I'm not sure if there is a better way to do this, but it took me awhile to figure out how to make this work correctly. In case anyone comes across this with the same issue:

import MKL_jll
ENV["MKLROOT"] = replace(MKL_jll.libmkl_rt_path,"libmkl_rt.so"=>"")
import GridapPardiso

But I also had to change the build.jl from mkllibdir = joinpath(mklroot,"lib/intel64") to mkllibdir = mklroot. I suppose, alternatively one could copy the libdir to somewhere that contains "lib/intel64" in the file path to avoid changing the backend.