Update libunwind to LLVM 19.1.4

[aheejin]

Other than these two PRs I submitted to upstream LLVM, all other changes are unrelated upstream changes.
llvm/llvm-project#92192
llvm/llvm-project#92840

This PR was created by running https://github.com/emscripten-core/emscripten/blob/main/system/lib/update_libunwind.py script.

[sbc100]

Are all these change from upstream or are there some new downstream patches too?

Did you already update the emscripten llvm-project fork?

Was this change created solely by system/lib/update_compiler_rt.py? If so can you mention that in the PR descirption?

Can you update system/lib/compiler-rt/readme.txt?

[aheejin]

Are all these change from upstream or are there some new downstream patches too?

Other than these two PRs I submitted to upstream LLVM, all other changes are unrelated upstream changes.
llvm/llvm-project#92192
llvm/llvm-project#92840

I updated the PR description too.

Did you already update the emscripten llvm-project fork?

I have created emscripten-libs-19 branch based on llvmorg-19.1.3 tag:
https://github.com/emscripten-core/llvm-project/tree/emscripten-libs-19
But I haven't uploaded the cherry-picking of our downstream patches onto that branch yet. I resolved conflicts, but given that that does not work here in Emscripten CI yet, I think that would need more fixes, so I thought I would upload them after fixing all CI failures here. Do you prefer to upload the apparent conflict-fixes first and then other fixes later to that branch?

Was this change created solely by system/lib/update_compiler_rt.py? If so can you mention that in the PR descirption?

Done.

Can you update system/lib/compiler-rt/readme.txt?

Done. I also updated ChangeLog.

[aheejin]

Given that 19.1.4 was released 10 hours ago(!), I'll probably update the version to that in this PR soon.

[sbc100]

lgtm once the tests pass!