Possible hang when stopping profiler

[armcknight]

Description

A customer reported a hang that BugSnag reports when our profiler is stopped while our SDK is not running. I was unable to reproduce the issue. The stack trace shows the following frames:

While investigating, I did notice that we potentially write a console log if stopping the thread fails, which contains a call to std::strerror:

sentry-cocoa/Sources/Sentry/SentrySamplingProfiler.cpp

Lines 164 to 165 in b2fea10

	SENTRY_ASYNC_SAFE_LOG_ERRNO_RETURN(pthread_cancel(thread_));
	SENTRY_ASYNC_SAFE_LOG_ERRNO_RETURN(pthread_join(thread_, NULL));

and the docs state that strerror is not thread safe, recommending using strerror_r instead. I'm not sure that is what's happening here, however; I would expect to see something related in the stack trace. We will look into changing that over in any case: #4190