Rebase on top of the LLVM-13 release commit

[XVilka]

See the tag:

• https://github.com/llvm/llvm-project/releases/tag/llvmorg-13.0.0
• https://github.com/llvm/llvm-project/commit/d7b669b3a30345cfcdb2fde2af6f48aa4b94845d

There are a few relevant changes ( https://releases.llvm.org/13.0.0/docs/ReleaseNotes.html#id5 )：

• Introduced assembly support for Armv9-A’s Realm Management Extension (RME) and Scalable Matrix Extension (SME).

[Phosphorus15]

This LLVM is now sync with the latest commit by far, i.e. 760d4d03d5d3fc0e0d6e4222f670e5fd068645f2