[clang] [llvm] [LinkerWrapper] Always pass `-flto` if the linker supports it (PR #102972)

[Joel E. Denny via cfe-commits]

jdenny-ornl wrote:

> Updated to pass `-O2` instead, this was the actual behavior that passed, so it's mostly not a functional change.

So you just changed the tests not to use -O1?  Doesn't this patch then represent a regression in what's supported?

(Rewriting history with force pushes make it harder to quickly spot what's changed since I looked before.  Can you not push new commits instead?)

https://github.com/llvm/llvm-project/pull/102972