Setup script ignores actual value of $ROS_DISTRO environment variable

[AlexSein98]

Per the ROS2 Humble installation instructions, I successfully installed Humble into ~/ros2_humble/. I then successfully ran the talker-listener demo.

Per a SpaceTeamsROS error message, I then set the $ROS_DISTRO environment variable, but it still didn't work. The error was:

Could not find /opt/ros/~/ros2_humble/setup.bash. Please check your ROS 2 installation.

After looking at the setup file, it seems like this sequence enforces that ROS can only be installed in /opt/ros/:

I'm going to change this to actually listen to the $ROS_DISTRO variable, since this currently directly conflicts with standard ROS installation instructions and will be confusing for new users. Additionally, I'll change the readme to include something about setting the $ROS_DISTRO environment variable.

[AlexSein98]

Seems like this might be caused by me building ROS from source, which I assumed was mandatory for development. This should support the built-from-source workflow anyway though, so I'll try to rewrite it to accommodate that as well.

[AlexSein98]

Actually I'm too dumb to figure this out, I just deleted the source build and got the debian build. Supporting source-built ROS is a TODO