[libc++abi] Avoid the warning: "__EXCEPTIONS" is not defined, evaluates to 0 [-Werror=undef]

Differential Revision: https://reviews.llvm.org/D108896

GitOrigin-RevId: ed4946fe20964509b27b38e74331c36857d4be53
diff --git a/include/__cxxabi_config.h b/include/__cxxabi_config.h
index cffedb8..05ed8b6 100644
--- a/include/__cxxabi_config.h
+++ b/include/__cxxabi_config.h
@@ -93,7 +93,7 @@
 #  if !__has_feature(cxx_exceptions)
 #    define _LIBCXXABI_NO_EXCEPTIONS
 #  endif
-#elif defined(_LIBCXXABI_COMPILER_GCC) && !__EXCEPTIONS
+#elif defined(_LIBCXXABI_COMPILER_GCC) && !defined(__EXCEPTIONS)
 #  define _LIBCXXABI_NO_EXCEPTIONS
 #endif