[llvm] [Inliner] Add option (default off) to inline all calls regardless of the cost (PR #152365)

[Nikita Popov via llvm-commits]

nikic wrote:

> For performance reasons, some users require that all calls be inlined. Rather than forcing them to adjust the inlining threshold to an arbitrarily high value, offer an option to inline all calls.

So is the intention here that end-users are going to do something like `-mllvm -inline-all-viable-calls=1`? Otherwise I'd expect this to be a frontend option that set `alwaysinline` on all functions.

https://github.com/llvm/llvm-project/pull/152365