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

[via cfe-commits]

eddyz87 wrote:

> > @eddyz87 ,
> > just create a new PR with the changes and make the cross references between this PR and the new one to let people easy find the original PR when necessary.
> 
> Yup, this is the typical process (GitHub doesn't let you reopen a merged PR).

Understood, thank you.
Will post the new pr.

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