[compiler-rt] [ARM][Compiler-RT] Add optional exclusion of libc provided ARM AEABI builtins from compiler-rt. (PR #137952)

[Simi Pallipurath via llvm-commits]

simpal01 wrote:

> I think it is worth mentioning in the description that libgcc does not define the aeabi functions that align with the C-library functions https://github.com/ARM-software/abi-aa/blob/main/rtabi32/rtabi32.rst#534memory-copying-clearing-and-setting so when this option is enabled then it will make compiler-rt match libgcc.
> 
> There is actually no `__aeabi_memcmp` function and neither clang or gcc call it. I don't know why compiler-rt defines it. I don't think it is worth removing it, but it does mean that we could exclude it, as it is logically a C-library provided function. I don't think it matters too much either way.
> 
> Also worth mentioning that this fixes a duplicate symbol problem when compiler-rt is added before the C-library on the link line, which is the case with the bare-metal driver.

Done

https://github.com/llvm/llvm-project/pull/137952