[llvm] [PowerPC][NFC] Allow different orders of .extern in some test cases (PR #89714)

[Felix via llvm-commits]

orcguru wrote:

Sure, let me dig out the root cause, and hope somebody can fix that.

[ExtSymSDNodeSymbols](https://reviews.llvm.org/D151335)
It's definition was: SmallPtrSet<MCSymbol *, 8> ExtSymSDNodeSymbols;

![New Note](https://github.com/llvm/llvm-project/assets/4339851/cdbca6b5-7d7d-48d7-ae92-217384db1bee)

Basically that's why we saw the reorder.

https://github.com/llvm/llvm-project/pull/89714