scripts: zephyr_flash_debug: teach runners a client/server abstraction

Several debugging scripts run setsid before executing a server
process, then run GDB with SIGINT ignored.

Relying on setsid is not portable. Add a popen_ignore_int() helper
that provides a portable alternative, and provide a generic
run_server_and_client() in ZephyrBinaryRunner which uses it to
abstract the pattern.

Subsequent patches will use this to implement the 'debug' command.

Signed-off-by: Marti Bolivar <marti.bolivar@linaro.org>
1 file changed