[llvm] Add target-byteorder for cases where endian in target triple is what matters (PR #107915)

[James Henderson via llvm-commits]

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@@ -1,5 +1,5 @@
 ; Avoid `!DL->isLittleEndian() && !CLI->enableBigEndian()` missmatch on PPC64BE.
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jh7370 wrote:

Is this comment still appropriate?

https://github.com/llvm/llvm-project/pull/107915