fix: rewrite Subcommand.run using Kernel.spawn

[doudou]

The current implementation was doing fork/exec by hand because it
had been created under ruby 1.8, which did not have spawn. It makes
zero sense nowadays, where there exists a multiplatform implementation
in the language itself.

[g-arjones]

Looks good and a very welcome change indeed. I'm curious though, what motivated this?

[doudou]

I'm having freezes during updates in CI in the ARM docker images (running qemu-arm-static). This is new, and it seems the system gets stuck in some of the pipe handling. I thought it might help (I'm kind of desperate - but I start to believe the problem is more emulation-related).

Did not solve the issue, and I honestly still don't know what happens. Thought it would be a pity to throw a nice cleanup commit like that, so there it is.

[planthaber]

@doudou we also see some freezes in CI with qemu->docker->arm, but this is (when I remember correctly) during compilation of ROS packages using catkin. We use autoproj to organize the workspace though (but not for the build).

I think that hints to an issue with the emulation rather than autobuild, as it is not used by autoproj when not buidling, right?

[doudou]

It actually is during import. But I more and more think it is an issue with QEmu indeed.

[planthaber]

It actually is during import.

I meant for us it is mostly compilation with catkin.

[doudou]

Closing this one, I have a new version along with a major cleanup of the file

FYI, newer QEmu versions seem to show this problem more rarely