Could we use this lib without intel MKL?

[jiacai2050]

Is your feature request related to a problem? Please describe.
When build vsag, we need to install intel MKL library, apparently this could only be used on x86, so I wonder:

1. Could we use this lib without MKL?
2. If yes, what disadvantages will it introduce? if no, I think we can list functions which rely on it, so others interested can contribute to make it doable.

[wxyucs]

@jiacai2050 I think it's possible now. VSAG depends on a BLAS backend and there are two choices in the library now (intel-mkl and openblas). When you build this library in an environment where cmake cannot find intel-mkl libraries, it will download openblas and use it as BLAS backend automatically.

DiskANN is the only thing that relies on a BLAS implementation. It uses BLAS to make matrix multiplication fast.