Export __asan_default_options for GCC

Unlike Clang 15, GCC 11 seems require default symbol visibility.

main.c

@@ -72,9 +72,11 @@ main(int argc, char **argv)
 /* Compile in the ASAN options Ruby needs, rather than relying on environment variables, so
  * that even tests which fork ruby with a clean environment will run ASAN with the right
  * settings */
+RUBY_SYMBOL_EXPORT_BEGIN
 const char *
 __asan_default_options(void)
 {
     return "use_sigaltstack=0:detect_leaks=0";
 }
+RUBY_SYMBOL_EXPORT_END
 #endif