superlu 5.0 should set $BLAS

[dingxiong]

"install-superlu.sh" says that if $BLAS is not equal to "SYSTEM", then it will resort to locally installed openblas. For people who have done apt-get install libopenblas-dev, maybe it is better to make it clear:
$export BLAS=SYSTEM && ./install-superlu.sh

[m-reuter]

What exactly do you mean? Where should this change be made? Thanks.