Disable the machine outliner by default
Disable the machine outliner by default

This addresses a codegen-issue that needs to be fixed upstream in LLVM.
While we wait for the fix, we can disable it.

Verified manually that the outliner is no longer run when
`-Copt-level=z` is specified, and also that you can override this with
`-Cllvm-args=-enable-machine-outliner` if you need it anyway.

A regression test is not really feasible in this instance, given that we
do not have any minimal reproducers.

Fixes #85351

aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust