Pass WITH_BLAS option from environment to CMake (#78037)
Allows to choose the BLAS backend with Eigen. Previously this was a CMake option only and the env variable was ignored.
Related to https://github.com/pytorch/pytorch/commit/f1f3c8b0fad9d647454a4d0507a2db4381563c8e
The claimed options BLAS=BLIS WITH_BLAS=blis are misleading: When BLAS=BLIS is set the WITH_BLAS option does not matter at all, it would only matter for BLAS=Eigen hence this issue went undetected so far.
Supersedes #59220
Pull Request resolved: https://github.com/pytorch/pytorch/pull/78037
Approved by: https://github.com/adamjstewart, https://github.com/janeyx99
