Add EngFlow to list of RE servers

[plaindocs]

Hey folks,

Disclaimer: I'm an EngFlow employee

I found this in my travels and thought I'd add to the list.

[nanonyme]

Has it been tested with this?

[plaindocs]

I believe so, but don't have a link to proof.

It's mentioned on the main website https://www.engflow.com/product/remoteExecution?r=menu****

I can ask around if you need something more specifc?

[nanonyme]

It's just that simply "Supports Remote Execution API's" has historically not been enough to mean it actually works due to various implementation details. Afaik there is no automated end-to-end testing in context of this project with EngFlow (assumably due to lack of testing cluster) so I was asking if that had been done by someone manually.

[abderrahim]

I can ask around if you need something more specifc?

I think the main thing buildstream needs is the ability to use the input root as the filesystem root. Like the chrootIntoInputRoot option of buildbarn.

Then some testing should indeed be in order just to validate that it indeed works.