Allows gen_snapshot to be built with asan in the Mojo tree.

runtime/bin/address_sanitizer.cc

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#include "platform/globals.h"
+
+#if defined(TARGET_OS_LINUX) || defined(TARGET_OS_MACOSX)
+#if defined(__has_feature)
+#if __has_feature(address_sanitizer)
+
+const char *kAsanDefaultOptions =
+    "strict_memcmp=0 symbolize=false check_printf=1 use_sigaltstack=1 "

[zra, 2015/02/12 23:13:38]

These are the same options used for Mojo asan builds. Do these look compatible
with what we do?

[koda, 2015/02/12 23:29:40]

They look safe enough. Consider using 0 rather than "false" for consistency.
Also, we need "handle_segv=0" to ensure our test harness correctly interprets
tests that are expected to crash by design.

[zra, 2015/02/13 00:11:19]

Changed to 0 and added handle_segv=0

+    "detect_leaks=0 fast_unwind_on_fatal=1 ";
+
+extern "C"
+__attribute__((no_sanitize_address))
+__attribute__((visibility("default")))
+// The function isn't referenced from the executable itself. Make sure it isn't
+// stripped by the linker.
+__attribute__((used))
+const char *__asan_default_options() {
+  return kAsanDefaultOptions;
+}
+
+#endif  // __has_feature(address_sanitizer)
+#endif  // defined(__has_feature)
+#endif  //  defined(TARGET_OS_LINUX) || defined(TARGET_OS_MACOSX)