[compiler-rt] [AArch64][compiler-rt] Add memcpy, memset, memmove, memchr simple imp… (PR #77496)

[Fangrui Song via llvm-commits]

MaskRay wrote:

> Patch co-authored by David Sherwood [david.sherwood at arm.com](mailto:david.sherwood at arm.com)

`Co-authored-by: ` needs to be at the line beginning https://docs.github.com/en/pull-requests/committing-changes-to-your-project/creating-and-editing-commits/creating-a-commit-with-multiple-authors

https://github.com/llvm/llvm-project/pull/77496