RFC: Integrate Arm Compute Library (ACL) as an in-tree module into oneDNN

[snadampal]

With oneDNN and ACL tightly coupled for aarch64 builds, having them in two repos is making it harder to keep the versions in sync. The request here is to bring ACL sources into oneDNN, may be as a git submodule.

This is a well known integration topic, that's why i'm not creating any detailed RFC document. I can create one if required.

[theComputeKid]

I recall this was discussed before with the oneDNN team and our current recommendation is for the developer to link against the latest release of ACL themselves rather than building in-source. Perhaps we can discuss this in person, to understand your requirements and pain points better.