test(oom): crash explicitly when malloc returns NULL

Raise an exception (Windows) or write to an invalid address (Unix)
when malloc fails, matching how UE terminates on OOM.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: jpnurmi

examples/example.c

@@ -387,7 +387,13 @@ trigger_oom(void)
     size_t count = 1024;
     for (;;) {
         void *p = malloc(count);
-        (void)p;
+        if (!p) {
+#ifdef SENTRY_PLATFORM_WINDOWS
+            RaiseException(0xc000, 0, 0, NULL);
+#else
+            *((volatile int *)3) = 1;
+#endif
+        }
         count *= 2;
     }
 }