[llvm] Migrate llvm-profdata to Opt flag parsing (PR #177868)

[David Zbarsky via llvm-commits]

dzbarsky wrote:

@petrhosek Thanks for taking a look - I updated per your comments in a separate commit but not sure if I did it properly, mind taking a look to see if it's what you intended?

https://github.com/llvm/llvm-project/pull/177868