[compiler-rt] [compiler-rt][AArch64] Allow platform-specific mangling of SME routines. (PR #119864)

[Jonas Devlieghere via llvm-commits]

JDevlieghere wrote:

This appears to break building compiler-rt on Apple Silicon: https://green.lab.llvm.org/job/llvm.org/view/LLDB/job/as-lldb-cmake/17192/console

```
/var/folders/nx/xsvw01q14kg11tbhjx5vgmr00000gn/T/sme-libc-mem-routines-b63f23.s:21:9: error: conditional branch requires assembler-local label. '.Lcopy_long' is external.
        b.hi .Lcopy_long
        ^
/var/folders/nx/xsvw01q14kg11tbhjx5vgmr00000gn/T/sme-libc-mem-routines-b63f23.s:23:9: error: conditional branch requires assembler-local label. '.Lcopy32_128' is external.
        b.hi .Lcopy32_128
        ^
/var/folders/nx/xsvw01q14kg11tbhjx5vgmr00000gn/T/sme-libc-mem-routines-b63f23.s:27:9: error: conditional branch requires assembler-local label. '.Lcopy16' is external.
        b.lo .Lcopy16
        ^
/var/folders/nx/xsvw01q14kg11tbhjx5vgmr00000gn/T/sme-libc-mem-routines-b63f23.s:36:9: error: Invalid relocation on conditional branch!
        tbz x2, 3, .Lcopy8
        ^
/var/folders/nx/xsvw01q14kg11tbhjx5vgmr00000gn/T/sme-libc-mem-routines-b63f23.s:46:9: error: Invalid relocation on conditional branch!
```

Can you please take a look and/or revert while this is being investigated?  

https://github.com/llvm/llvm-project/pull/119864