Pull compact-unwind support into llvm-20 (2nd attempt)

[lhames]

We should pull ORC compact-unwind support into LLVM 20. This is needed to support JIT'd exceptions and stack unwinding on M1 Macs.

These patches only touch ORC / JITLink (and associated test tools), and only change behavior for JIT'd code on Darwin.

/cherry-pick 7fb233f a1ff2d1 b46211b c0f7ebe b84ac58 52b5e36 9de581b eae6d6d aefa30e 88f55d1 4a2a8ed 9d88ffe 7a213e7 e00f824 7811c20 63bb4ba e2eaf8d

[lhames]

Previous request was made in #126013, but was missing some commits.

[llvmbot]

/pull-request #126361

[llvmbot]

@llvm/issue-subscribers-orcjit

Author: Lang Hames (lhames)

We should pull ORC compact-unwind support into LLVM 20. This is needed to support JIT'd exceptions and stack unwinding on M1 Macs.

These patches only touch ORC / JITLink (and associated test tools), and only change behavior for JIT'd code on Darwin.

/cherry-pick 7fb233f a1ff2d1 b46211b c0f7ebe b84ac58 52b5e36 9de581b eae6d6d aefa30e 88f55d1 4a2a8ed 9d88ffe 7a213e7 e00f824 7811c20 63bb4ba e2eaf8d