In order to be consistent between Gazebo and jMAVSim we should be using
the env variable PX4_SIM_SPEED_FACTOR in the same way. This enables
vscode to set the speed using the env variable.
This updates the jMAVSim submodule which includes a fix for HITL.
In order to fix HITL, a CLI argument `-lockstep` was required to enable
lockstep. This has now been added to the command in jmavsim_run.sh.
This checks if we are on macOS and if we have Java 8 installed. If yes,
it falls back to Java 8 by setting JAVA_HOME.
This avoids https://github.com/PX4/jMAVSim/issues/81
It is useful to run jmavsim separately, for example when debugging mainapp
separately, or running some other external tool on mainapp (like heap
analysis)