When are pipeline variables like buildWPF set?

[mitchcapper]

Essentially trying to figure out when the CI does or does not build conpty, wpf, etc? I looked at the source and didn't see what in the pipeline sets them. I couldn't even see how to see the variables a pipeline run was executed with.

Fun pipelines feature:
If you click view pipeline it prompts for login and for non MSFT it says 401 - Uh-oh, you do not have access. which alright, but once you do you need to clear cookies to view any of the pipeline again as now all pages return that (even those that were public before):)

More fun is if you just login (so it shows you logged in at the upper right) you can still browse but as soon as you click view pipelines that is when it stops working for any page. Found that quirk when going to report the sign in resulting in less access issue (clicking the ? and report a bug at the top) it gave the 401 error, and then had me signed into the CI site, but I could browse (until viewing a pipeline exploded it all).