[libunwind] [libunwind][AIX] Remove weak definition "__xlcxx_personality_v0" (PR #112436)

[Hubert Tong via cfe-commits]

https://github.com/hubert-reinterpretcast commented:

I think a small test case could be added with a `int main(void) {}` C program linked with -`brtl` and `LDR_PRELOAD`/`LDR_PRELOAD64` set to `libunwind.a(libunwind.so.1)`.

https://github.com/llvm/llvm-project/pull/112436