[libunwind] [libunwind][PPC64] Fix _Unwind_Backtrace SIGSEGV from TOC restore at end of stack on LE (PR #212142)

[Piotr Kubaj via cfe-commits]

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@@ -22,6 +22,15 @@
 #include "dwarf2.h"
 #include "libunwind_ext.h"
 
+#if defined(_LIBUNWIND_TARGET_PPC64) && defined(__BYTE_ORDER__) &&             \
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pkubaj wrote:

Right, this is about ABI, not endianness. The original patch was only for LE, because the crash actually doesn't happen on BE. I switched the guard to defined(_CALL_ELF) && _CALL_ELF == 2 and renamed the flag _unw_ppc64_in_backtrace.

https://github.com/llvm/llvm-project/pull/212142