Switch local launching of debugserver over to always use a FIFO in order to handshake with the launched debugserver.

This helps ensure that the launched debugserver is ready and listening for a connection. Prior to this we had a race condition.

Consolidate the launching of debugserver into a single place: a static function in GDBRemoteCommunication.



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@196401 91177308-0d34-0410-b5e6-96231b3b80d8