gh-127604: Only define dump_pointer() if CAN_C_BACKTRACE (#132897)

Python/traceback.c

@@ -879,12 +879,14 @@ _Py_DumpHexadecimal(int fd, uintptr_t value, Py_ssize_t width)
     dump_hexadecimal(fd, value, width, 0);
 }
 
+#ifdef CAN_C_BACKTRACE
 static void
 dump_pointer(int fd, void *ptr)
 {
     PUTS(fd, "0x");
     dump_hexadecimal(fd, (uintptr_t)ptr, sizeof(void*), 1);
 }
+#endif
 
 static void
 dump_char(int fd, char ch)