[compiler-rt] [llvm] [InstrFDO]Record the on-disk header size in indexed profile header (PR #88212)

[Mingming Liu via llvm-commits]

minglotus-6 wrote:

Discussed this approach with Snehasish. My takeaway is there should be a way to detect semantic changes of existing payload sections and require a profile reader update, if this change is going to allow profile reader to parse unknown newer versions. Going to convert this to draft and work on a solution.

https://github.com/llvm/llvm-project/pull/88212