Allow the hostname to be specified when asking a platform to launch another debugserver in case you want to change it.

The GDB server remote platform how has the debugserver that are launched on iOS devices to use localhost due to the use of a USB mux.



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@196405 91177308-0d34-0410-b5e6-96231b3b80d8