[libcxxabi] Fix test_exception_address_alignment test for ARM

[yroux]

Summary

Check _LIBCXXABI_ARM_EHABI macro instead of libunwind version.

Fixes PR34182

[mclow.lists]

That certainly *looks* more correct to me.

[hans]

What do you other reviewers say? I'm not familiar with this code, but this seems reasonable to me.

[yroux]

I dug a bit and can give more context. The usage of _LIBUNWIND_ARM_EHABI was introduced by D31178 but from what we are seeing with the release builds, libunwind headers are not picked up (at least in these configs) and since r309226 was committed, clang and libunwind unwind.h versions are close enough (and are the same w/r to alignment) to rely on libcxxabi macro _LIBCXXABI_ARM_EHABI to choose the alignment no matter which unwind header is used.

[hans]

It doesn't seem to get more reviewed than this.

yroux, I'd say go ahead and commit it.

libcxxabi/trunk/test/test_exception_address_alignment.pass.cpp

 // working around this failure.
 // XFAIL: darwin && libcxxabi-has-system-unwinder
 
 // Test that the address of the exception object is properly aligned as required
 // by the relevant ABI
 
 #include <cstdint>
 #include <cassert>
+#include <__cxxabi_config.h>
 
 #include <unwind.h>
 
 struct __attribute__((aligned)) AlignedType {};
 
 // EHABI  : 8-byte aligned
 // Itanium: Largest supported alignment for the system
-#if defined(_LIBUNWIND_ARM_EHABI)
+#if defined(_LIBCXXABI_ARM_EHABI)
 #  define EXPECTED_ALIGNMENT 8
 #else
 #  define EXPECTED_ALIGNMENT alignof(AlignedType)
 #endif
 
 static_assert(alignof(_Unwind_Exception) == EXPECTED_ALIGNMENT,
   "_Unwind_Exception is incorrectly aligned. This test is expected to fail");