tsan: profiler data races on Mac

[rmacnak-google]

WARNING: ThreadSanitizer: data race (pid=6565)
  Write of size 8 at 0x000108f0c8c0 by thread T4:
    #0 dart::Thread::set_current_tag(dart::UserTag const&) <null> (dartvm:arm64+0x10054f620)
    #1 dart::Dart::InitializeIsolate(dart::Thread*, bool, void*) <null> (dartvm:arm64+0x10035dcd4)
    #2 dart::CreateIsolate(dart::IsolateGroup*, bool, char const*, void*, char**) <null> (dartvm:arm64+0x1008a235c)
    #3 Dart_CreateIsolateGroup <null> (dartvm:arm64+0x1008a280c)
    #4 dart::bin::CreateIsolateGroupAndSetup(char const*, char const*, char const*, char const*, Dart_IsolateFlags*, void*, char**) <null> (dartvm:arm64+0x1000058e0)
    #5 dart::RunServiceTask::Run() <null> (dartvm:arm64+0x100531394)
    #6 dart::ThreadPool::WorkerLoop(dart::ThreadPool::Worker*) <null> (dartvm:arm64+0x100557410)
    #7 dart::ThreadPool::Worker::Main(unsigned long) <null> (dartvm:arm64+0x100557834)
    #8 dart::ThreadStart(void*) <null> (dartvm:arm64+0x1004d01bc)

  Previous read of size 8 at 0x000108f0c8c0 by thread T2 (mutexes: write M0):
    #0 dart::Profiler::SampleThread(dart::Thread*, dart::InterruptedThreadState const&) <null> (dartvm:arm64+0x1004d7070)
    #1 dart::ThreadInterrupter::InterruptThread(dart::OSThread*) <null> (dartvm:arm64+0x100556424)
    #2 dart::ThreadInterrupter::ThreadMain(unsigned long) <null> (dartvm:arm64+0x100555f64)
    #3 dart::ThreadStart(void*) <null> (dartvm:arm64+0x1004d01bc)

log

WARNING: ThreadSanitizer: data race (pid=16029)
  Write of size 8 at 0x00010d3046a8 by main thread:
    #0 dart::Thread::ExitIsolate(bool) <null> (dartvm:arm64+0x10054ffec)
    #1 dart::Dart::DartInit(Dart_InitializeParams const*) <null> (dartvm:arm64+0x10035c23c)
    #2 dart::Dart::Init(Dart_InitializeParams const*) <null> (dartvm:arm64+0x10035c334)
    #3 Dart_Initialize <null> (dartvm:arm64+0x1008a1a34)
    #4 dart::bin::main(int, char**) <null> (dartvm:arm64+0x1000051e8)
    #5 main <null> (dartvm:arm64+0x100004084)

  Previous read of size 8 at 0x00010d3046a8 by thread T2 (mutexes: write M0):
    #0 dart::Thread::IsExecutingDartCode() const <null> (dartvm:arm64+0x100552214)
    #1 dart::Profiler::SampleThread(dart::Thread*, dart::InterruptedThreadState const&) <null> (dartvm:arm64+0x1004d6f28)
    #2 dart::ThreadInterrupter::InterruptThread(dart::OSThread*) <null> (dartvm:arm64+0x100556424)
    #3 dart::ThreadInterrupter::ThreadMain(unsigned long) <null> (dartvm:arm64+0x100555f64)
    #4 dart::ThreadStart(void*) <null> (dartvm:arm64+0x1004d01bc)

log