Bug 1754474 - Add a suppresion for the Glean init thread. r=decoder

The init/shutdown sequence and its threads
are being re-evaluated as part of bug 1755449

Depends on D138466

Differential Revision: https://phabricator.services.mozilla.com/D138767

mozglue/build/TsanOptions.cpp

@@ -296,6 +296,11 @@ extern "C" const char* __tsan_default_suppressions() {
          "race:js::wasm::Code::setTier2\n"
          "race:js::wasm::Code::setAndBorrowTier2\n"
 
+         // Bug 1755449
+         // The Glean init thread is used to perform I/O and other blocking operations.
+         // It is never joined with the main thread, but this is being re-evaluated.
+         "thread:glean::initialize\n"
+
       // End of suppressions.
       ;  // Please keep this semicolon.
 }