We see a lot of errors

/jdk-dev/src/java.desktop/share/native/libharfbuzz/hb-algs.hh:882:10: error: 1540-2993 The builtin "__builtin_mul_overflow" is not supported.

Seems xlC sets the clang related macros, so we run into __builtin_mul_overflow , we might need to avoid this and add special handling for AIX

878 #if (defined(__GNUC__) && (__GNUC__ >= 4)) || (defined(__clang__) && (__clang_major__ >= 8))
879 unsigned stack_result;
880 if (!result)
881 result = &stack_result;
882 return __builtin_mul_overflow (count, size, result);
883 #endif