Fix triggers

Fix triggers

The github triggers were broken with two types of windows builds using the same context next.  One was the build only job that is just used to feed into the *Nix testing.  We don't need to launch these builds at all, since they are just used for internal testing.

See also dotnet/coreclr#3475

Commit migrated from https://github.com/dotnet/coreclr/commit/2a9a7f1574e140199ac461882f4b4b0fe4be9672