Fix TestConcurrentEvents to behave nicely with GCC 4.8
- newer gcc generates additional debuginfo for function exit (stack object desctruction) which was causing tests to fail
- work-around consists of not declaring any stack objects in main()



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@187389 91177308-0d34-0410-b5e6-96231b3b80d8