- fixes #10925

FlightTaskAutoLine: ensure that desired speed along track does not exceed maximum speed at threshold to target

Smoothing can be configured by MPC_POS_MODE parameter
put before only for position mode and not for altitude mode.

    - sitl_gazebo in PX4/Firmware (dcd12b5f): https://github.com/PX4/sitl_gazebo/commit/5a50cb9a52737522b28abf14ce15b57de8ff2695
    - sitl_gazebo current upstream: https://github.com/PX4/sitl_gazebo/commit/7c97eeae139d86b3747ea877d8067fb3180dc4f1
    - Changes: https://github.com/PX4/sitl_gazebo/compare/5a50cb9a52737522b28abf14ce15b57de8ff2695...7c97eeae139d86b3747ea877d8067fb3180dc4f1

 - explicitly set TOOLCHAIN on all NuttX targets

launch script for jmavsim failed to start if there were any spaces in
paths, string handling in paths was improved and tested.

*  a request for setting the '_HASH_CHECK' parameter is handled differently
than the same request for a standard parameter. Make sure we don't actually
try to set the parameter.

Signed-off-by: Roman <bapstroman@gmail.com>

Co-Authored-By: CUAVcaijie <caijie@cuav.net>