[llvm] [llvm-objcopy] Add llvm-objcopy option --set-symbol-visibility (PR #80872)

[Fangrui Song via llvm-commits]

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@@ -450,6 +450,15 @@ them.
  Set the start address of the output to ``<addr>``. Overrides any previously
  specified :option:`--change-start` or :option:`--adjust-start` options.
 
+.. option:: --set-symbol-visibility <symbol>=<visibility>
+
+ Change the visibility of a symbol to the specified value.
+
+.. option:: --set-symbols-visibility <filename>=<visibility>
+
+ Reads a list of symbols from <filename> and changes their visibility to the
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MaskRay wrote:

Yes, there are ~8 options that are inconsistent with others. Actually there is a larger problem that many help messages have not be synced with the clearer semantics: llvm/docs/CommandGuide/llvm-objcopy.rst

I am working on a patch to fix these help messages.

For the new options, definitely use imperative sentences as llvm/docs/CommandGuide/llvm-objcopy.rst uses.

https://github.com/llvm/llvm-project/pull/80872