Bug 1590423 - Suppress races related to Rust std::sync::Arc. r=jseward

Differential Revision: https://phabricator.services.mozilla.com/D50078

--HG--
extra : moz-landing-system : lando

mozglue/build/TsanOptions.cpp

@@ -75,6 +75,9 @@ extern "C" const char* __tsan_default_suppressions() {
          // Bug 1587513
          "race:std::sync::mutex::Mutex\n"
 
+         // Bug 1590423
+         "race:sync..Arc\n"
+
       // End of suppressions.
       ;  // Please keep this semicolon.
 }