internal/ci: ensure internal/_e2e isn't broken in CI

I have broken the build of the internal/_e2e tests more than once,
most recently fixed in https://cuelang.org/cl/1198297,
as we only actually run these tests on pushes to protected branches.

However, it's easy to build the tests in a CI run before merging,
and that will catch most of these mistakes which can happen as a result
of refactors or other API changes which internal/_e2e uses.

Signed-off-by: Daniel Martí <mvdan@mvdan.cc>
Change-Id: I529ed3b1d52e86ef1f9c41744ebc2d97ef3d77a2
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1198300
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Reviewed-by: Paul Jolly <paul@myitcv.io>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>

.github/workflows/trybot.yml

@@ -146,6 +146,7 @@ jobs:
         run: |-
           go vet ./...
           go mod tidy
+          (cd internal/_e2e && go test -run=-)
       - if: always()
         name: Check that git is clean at the end of the job
         run: test -z "$(git status --porcelain)" || (git status; git diff; false)

internal/ci/github/trybot.cue

@@ -158,12 +158,17 @@ workflows: trybot: _repo.bashWorkflow & {
 		// However, CUE does not have any such build tags yet, and we don't use
 		// dependencies that vary wildly between platforms.
 		// For now, to save CI resources, just run the checks on one matrix job.
+		//
+		// Also ensure that the end-to-end tests in ./internal/_e2e, which are only run
+		// on pushes to protected branches, still build correctly before merging.
+		//
 		// TODO: consider adding more checks as per https://github.com/golang/go/issues/42119.
 		if:   "\(_isLatestLinux)"
 		name: "Check"
 		run: """
 			go vet ./...
 			go mod tidy
+			(cd internal/_e2e && go test -run=-)
 			"""
 	}