internal/ci: allow gerritHubHostname to be overridden

This will allow us to experiment with an alternative GerritHub host in
other repos that depend on this internal/ci CUE module.

Signed-off-by: Paul Jolly <[email protected]>
Change-Id: I692f4416b98b4743941199f6068d9106a7443c5b
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1218940
TryBot-Result: CUEcueckoo <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>

Author: myitcv

internal/ci/base/base.cue

@@ -37,7 +37,7 @@ import (
 // Package parameters
 githubRepositoryPath: *(URLPath & {#url: githubRepositoryURL, _}) | string
 githubRepositoryURL:    *("https://github.com/" + githubRepositoryPath) | string
-gerritHubHostname:      "review.gerrithub.io"
+gerritHubHostname:      *"review.gerrithub.io" | string
 gerritHubRepositoryURL: *("https://\(gerritHubHostname)/a/" + githubRepositoryPath) | string
 trybotRepositoryPath:   *(githubRepositoryPath + "-" + trybot.key) | string
 trybotRepositoryURL:    *("https://github.com/" + trybotRepositoryPath) | string