[llvm] [llvm-readobj] enable demangle option for the xcoff object file (PR #78455)

[James Henderson via llvm-commits]

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@@ -56,6 +56,11 @@ file formats.
 
  Display the address-significance table.
 
+.. option:: --demangle, -C
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jh7370 wrote:

`--no-demangle` still needs adding.

https://github.com/llvm/llvm-project/pull/78455