Add workaround for iohandler races on FreeBSD

[emaste]

Summary

We encounter issues from iohandler races very commonly on FreeBSD. This workaround is already in the version of LLDB in the FreeBSD tree. It's not pretty but is a significant usability improvement in the short term.

Related PR https://llvm.org/bugs/show_bug.cgi?id=14637

[emaste]

Proper fix in D9823. This can be abandoned once it is in.

[emaste]

Proper change committed in rL238313

source/Target/Process.cpp

if (error.Success())
                 log->Printf ("Process::PrivateResume() asked to simulate a start & stop.");
             
             SetPrivateState(eStateRunning);
             SetPrivateState(eStateStopped);
         }
     }
     else if (log)
         log->Printf ("Process::PrivateResume() got an error \"%s\".", error.AsCString("<unknown error>"));
+#ifdef __FreeBSD__
+    /* XXX work around IoHandler races */
+    ::usleep(100);
+#endif
     return error;
 }
 
 Error
 Process::Halt (bool clear_thread_plans)
 {
     // Don't clear the m_clear_thread_plans_on_stop, only set it to true if
     // in case it was already set and some thread plan logic calls halt on its