When testing terminal-mode applications using lldb-vscode on macOS, it's
currently required to set LLDB_LAUNCH_FLAG_LAUNCH_IN_TTY when starting
lldb-vscode so that the application launches in a new Terminal.app
window. This is unlikely to work for VSCode as there's no obvious way to
vscode-cpptools uses externalConsole: true to enable this behaviour,
so we implement the same here .