[llvm] [clang] [llvm][ARM] Emit MVE .arch_extension after .fpu directive if it does not include MVE features (PR #71545)

[David Spickett via cfe-commits]

DavidSpickett wrote:

Just small things on the test case from me. Nominate @davemgreen to give it a final check and approval, since I have not been around this area in a while.

https://github.com/llvm/llvm-project/pull/71545