Fix unwind registration for multiple JIT instances in a single process. (2nd attempt)

[lhames]

/cherry-pick 84fe1f6 9f61a60

This is the fix for #126611. It only affects ORC, and only changes behavior when used with libunwind (so primarily on Darwin and BSD, but some Linux clients too).

This issue supersedes #126824, and includes a follow-up patch to fix an unused variable warning.

[llvmbot]

@llvm/issue-subscribers-jitlink

Author: Lang Hames (lhames)

/cherry-pick 84fe1f6 9f61a60

This is the fix for #126611. It only affects ORC, and only changes behavior when used with libunwind (so primarily on Darwin and BSD, but some Linux clients too).

This issue supersedes #126824, and includes a follow-up patch to fix an unused variable warning.

[llvmbot]

@llvm/issue-subscribers-orcjit

Author: Lang Hames (lhames)

/cherry-pick 84fe1f6 9f61a60

This is the fix for #126611. It only affects ORC, and only changes behavior when used with libunwind (so primarily on Darwin and BSD, but some Linux clients too).

This issue supersedes #126824, and includes a follow-up patch to fix an unused variable warning.

[llvmbot]

/pull-request #126831