[libcxxabi] Check __SEH__, when checking if ARM EHABI is implied

ARM EHABI isn't signalled by any specific compiler builtin define,
but is implied by the lack of defines specifying any other
exception handling mechanism, `__USING_SJLJ_EXCEPTIONS__` or
`__ARM_DWARF_EH__`.

As Windows SEH also can be used for unwinding, check for the
`__SEH__` define too, in the same way.

Differential Revision: https://reviews.llvm.org/D126866

NOKEYCHECK=True
GitOrigin-RevId: 4a3722a2c3dff1fe885cc38bf43d3c095c9851e7
diff --git a/include/__cxxabi_config.h b/include/__cxxabi_config.h
index 11a74db..c97dd65 100644
--- a/include/__cxxabi_config.h
+++ b/include/__cxxabi_config.h
@@ -10,7 +10,7 @@
 #define ____CXXABI_CONFIG_H
 
 #if defined(__arm__) && !defined(__USING_SJLJ_EXCEPTIONS__) &&                 \
-    !defined(__ARM_DWARF_EH__)
+    !defined(__ARM_DWARF_EH__) && !defined(__SEH__)
 #define _LIBCXXABI_ARM_EHABI
 #endif