Add ros_environment

[kjeremy]

So that we can get to ROS_DISTRO at build time.

See: lopsided98/nix-ros-overlay#406

[kjeremy]

The build failures seem unrelated.

[sktometometo]

Let me check why this package is necessary with more details so that the maintainer (@k-okada ) can easily understand the situation since he is so busy.

ROS_DISTRO is already set when building the package with catkin on ubuntu. So I think that's why we haven't needed ros_environment package before.
I don't know much about your project. What is the aim of the project and why there is such difference when building this package?

[kjeremy]

@sktometometo we are building using https://github.com/lopsided98/nix-ros-overlay on NixOS. The wiki page for ros_environment states that it provides ROS_DISTRO, ROS_VERSION etc.

REP 149 states:

A new ROS package named ros_environment which has minimal dependencies will be available in both ROS versions and providing the new environment variables as well as some of the existing environment variables.

Also see this https://answers.ros.org/question/286969/use-identical-packagexml-for-ros1-and-ros2-pkgs/