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

[James Henderson via llvm-commits]

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jh7370 wrote:

The norm for new options is to have a single test that test the different cases rather than lots of individual test files. This makes it easier to understand the option's full behaviour because you don't have to look through multiple files to understand everything. If you need different input files for different cases, you can use the yaml2obj `--docnum` option or possibly the `-D` option to set macro values, whichever is more appropriate. Sometimes you can get away with only one input and have multiple symbols in it with appropriate properties.

Also nit: please don't start your file with a blank line :)

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