[llvm] [BPF] Define empty set of BPF libcalls (PR #169537)

[Lucas Ste via llvm-commits]

LucasSte wrote:

> Relatedly, we need to treat the set of available functions as a dynamic program property which is what I've been working towards.

Does this mean programs will decide which library functions are available to them?

https://github.com/llvm/llvm-project/pull/169537