Build as an overlay on Windows/Linux

[theseankelly]

• Updated repos file to build as an overlay
• Upated build instructions
• Created a Linux build workflow

Closes #51
Closes #53
Closes #55

[theseankelly]

Ugh building in CI has been one of the most frustrating topics...I've been testing over in my private fork for over a week (with all passes yesterday) and all I did differently was submit a PR. I'll keep working on it I guess.

https://github.com/theseankelly/ros2_dotnet/actions

[esteve]

@theseankelly is there anything I can help with?

[theseankelly]

@esteve thanks, but I don't think so -- in theory it should be straightforward. I think GitHub Actions is inserting some entropy just to troll me.

[theseankelly]

Wow, talk about poor timing.

The Windows runner for GitHub actions was refreshed very recently, which updated the default system Python to 3.7.7. It looks like the ros-tooling/setup-ros action hardcodes Python 3.7.6, which is now broken.

I filed a bug on the ros-tooling/setup-ros action, but its easily worked around by configuring python 3.7.6 prior to invoking the ros-tooling/setup-ros action.

Looks like the Build (Desktop) job has made it farther this time -- fingers crossed.

[esteve]

@theseankelly yay, the desktop runner passed! Thanks

[esteve]

@theseankelly is this ready for review or you'd rather way for the fix in ros-tooling/setup-ros ?

[theseankelly]

@esteve let's go ahead with the review as-is.

[esteve]

@theseankelly thanks!