Fix libmemunreachable vs hwasan conflict.

* Scan memory in a non-sanitized function.
* Don't scan hwasan shadow mappings.
  Shadow is ~33G and never contains any heap pointers. The scan takes
  about a minute on my device.

Bug: 112438058
Test: memunreachable_test with SANITIZE_TARGET=hwaddress
      the test still fails, but now there are no hwasan reports or new
      tombstones, and it completes in less than a minute

Change-Id: Ibe4811c67609ca9fe317edc250993b915570a638
diff --git a/libmemunreachable/MemUnreachable.cpp b/libmemunreachable/MemUnreachable.cpp
index 3d7b8a8..299c320 100644
--- a/libmemunreachable/MemUnreachable.cpp
+++ b/libmemunreachable/MemUnreachable.cpp
@@ -217,6 +217,10 @@
   return ret == 0;
 }
 
+static bool is_sanitizer_mapping(const allocator::string& s) {
+  return s == "[anon:low shadow]" || s == "[anon:high shadow]" || has_prefix(s, "[anon:hwasan");
+}
+
 bool MemUnreachable::ClassifyMappings(const allocator::vector<Mapping>& mappings,
                                       allocator::vector<Mapping>& heap_mappings,
                                       allocator::vector<Mapping>& anon_mappings,
@@ -258,7 +262,8 @@
     } else if (mapping_name.size() == 0) {
       globals_mappings.emplace_back(*it);
     } else if (has_prefix(mapping_name, "[anon:") &&
-               mapping_name != "[anon:leak_detector_malloc]") {
+               mapping_name != "[anon:leak_detector_malloc]" &&
+               !is_sanitizer_mapping(mapping_name)) {
       // TODO(ccross): it would be nice to treat named anonymous mappings as
       // possible leaks, but naming something in a .bss or .data section makes
       // it impossible to distinguish them from mmaped and then named mappings.