Enables build with oneDNN (MKL-DNN) on AArch64 (#50400)
Summary:
Since version 1.6, oneDNN has provided limited support for AArch64 builds.
This minor change is to detect an AArch64 CPU and permit the use of
`USE_MKLDNN` in that case.
Build flags for oneDNN are also modified accordingly.
Note: oneDNN on AArch64, by default, will use oneDNN's reference C++ kernels.
These are not optimised for AArch64, but oneDNN v1.7 onwards provides support
for a limited set of primitives based Arm Compute Library.
See: https://github.com/oneapi-src/oneDNN/pull/795
and: https://github.com/oneapi-src/oneDNN/pull/820
for more details. Support for ACL-based oneDNN primitives in PyTorch
will require some further modification,
Fixes #{issue number}
Pull Request resolved: https://github.com/pytorch/pytorch/pull/50400
Reviewed By: izdeby
Differential Revision: D25886589
Pulled By: malfet
fbshipit-source-id: 2c81277a28ad4528c2d2211381e7c6692d952bc1
