Allow to pass an executable file via lldb-mi arguments (MI)

Summary:
# Allow to pass an executable file via lldb-mi arguments
# Add tests
# Fix (gdb) prompt in CMIDriver::LocalDebugSessionStartupExecuteCommands
# Fix prompt in CMIDriver::InterpretCommandThisDriver: use the lldb-mi prompt instead of a hard-coded value.

All tests pass on OS X.

Reviewers: abidh, clayborg

Reviewed By: clayborg

Subscribers: lldb-commits, clayborg, abidh

Differential Revision: http://reviews.llvm.org/D8001

llvm-svn: 231070