This adds the option to build Qt with libb2, which is especially
recommended, if you care about the performance of the BLAKE2 hashing
algorithms. The bundled version is the pure reference C implementation
of BLAKE2, while libb2 has many additional hardware optimizations.
However, the API of both is the same, so no changes to the code were
necessary here.
Change-Id: I3563982f4e07be300291fe103c38b16a404b3ebb
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
