[llvm] [llvm-objdump] Implement decoding auxiliary header for xcoff with llvm-objdump --private-headers (PR #105682)

[zhijian lin via llvm-commits]

================
@@ -0,0 +1,128 @@
+## Test that `the llvm-objdump --private-headers` print out the auxiliary header of XCOFF object file.
----------------
diggerlin wrote:

yes, I think so.

https://github.com/llvm/llvm-project/pull/105682