Added a basic connection test for lldb-gdbserver.

The lldb-gdbserver tests are skipped if the lldb-gdbserver exe cannot be found (currently only built for Linux and FreeBSD).  The lldb-gdbserver exe is found by the LLDB_EXEC environment variable, using the same dir as the lldb exe, and then replacing lldb with lldb-gdbserver.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@206731 91177308-0d34-0410-b5e6-96231b3b80d8