Fix caffe2 build with BLAS=OpenBLAS (#18422)
Summary:
g++ complains about failing to find the declaration of cblas_sscal and cblas_dscal BLAS function
let's fix it :)
fedora 29, gcc 8.3.1, openblas 0.3.5
build with cmake -DBLAS=OpenBLAS ..
Pull Request resolved: https://github.com/pytorch/pytorch/pull/18422
Differential Revision: D14598977
Pulled By: soumith
fbshipit-source-id: bde77bfb359d2ff38226401caeed78c114ef7468
