add 'nodiscard' attribute to mimalloc interface

src/options.c

@@ -85,7 +85,7 @@ void _mi_options_init(void) {
   mi_add_stderr_output(); // now it safe to use stderr for output
   for(int i = 0; i < _mi_option_last; i++ ) {
     mi_option_t option = (mi_option_t)i;
-    mi_option_get(option); // initialize
+    long l = mi_option_get(option); UNUSED(l); // initialize
     if (option != mi_option_verbose) {
       mi_option_desc_t* desc = &options[option];
       _mi_verbose_message("option '%s': %ld\n", desc->name, desc->value);