[clang] [llvm] [BPF] introduce `__attribute__((bpf_fastcall))` (PR #101228)

[via cfe-commits]

eddyz87 wrote:

@AaronBallman, could you please help me with the procedural question:
I reverted the commit and current pull request is now closed, what should I do when I'll figure out the fix?
It looks like there is no option to re-open pull request, hence it looks like I will have to open a new pull request.

https://github.com/llvm/llvm-project/pull/101228