aspnetcore isn't building installers in the VMR

[ViktorHofer]

The BuildInstallers switch defines if installers should be built which defaults to false. We should pass the switch in here: https://github.com/dotnet/dotnet/blob/eb82b31516b032924126ac2c81f3edca80911619/repo-projects/aspnetcore.proj#L12

-buildinstallers (Unix) / - BuildInstallers (Windows)

Note that there's also a join point on Windows in the installers which will fail the Windows dev leg when it gets enabled: dotnet/aspnetcore#52884

cc @jkoritzinsky @NikolaMilosavljevic

[jkoritzinsky]

I'm working on re-writing aspnetcore's installer infra to be based on the Arcade tooling as we speak. I'll take this on once I finish the rewrite.

[ViktorHofer]

The Windows part is now completed. @jkoritzinsky will continue working on the Unix part when he's back.