[libunwind] [libunwind][Haiku] Fix signal frame unwinding (PR #135367)

[Trung Nguyen via cfe-commits]

trungnt2910 wrote:

Tried to give [x86 unwinding](https://github.com/trungnt2910/libunwind-haiku/commit/61a36e3d8ed6da29653bba63165093cadc53333) a shot. The general idea is correct, but it is currently impossible to unwind past a `syscall` due to the system relying on another [magic `commpage` function](https://github.com/haiku/haiku/blob/742a3c335974346617b0869007eb2fb5324465bb/src/system/kernel/arch/x86/32/syscalls_asm.S#L22) without saving the context.

https://github.com/llvm/llvm-project/pull/135367