[scudo] Fix buildbot test error on ARM

[cryptoad]

Summary

The assumption __sanitizer_get_heap_size() == 0 (introduced in D29341) at the
start of a program appears to be incorrect on some ARM machines
(SizeClassAllocator32).

This should fix the test while I investigate the issue.

[cryptoad]

Actual diff.

[alekseyshl]

LGTM

test/scudo/interface.cpp

for (size_t size : sizes) {
       assert(p);
       assert(__sanitizer_get_ownership(p));
       assert(__sanitizer_get_allocated_size(p) >= size);
       free(p);
     }
   }
   if (!strcmp(argv[1], "heap-size")) {
     // Ensures that __sanitizer_get_heap_size can be called before any other
-    // allocator function. At this point, this heap size should be 0.
-    assert(__sanitizer_get_heap_size() == 0);
+    // allocator function.
+    assert(__sanitizer_get_heap_size() >= 0);
   }
 
   return 0;
 }