internal/ci: run long tests on linux when testing CLs

It's too easy to forget that CUE_LONG exists,
particularly since it is rarely used by our tests,
and CI enables it when testing master but not when testing CLs.

Enable it when testing CLs as well.
However, since Windows is particularly slow to run,
and we need the trybots to be reasonably fast to iterate on CLs,
we only enable it on CLs for the "latest linux" matrix cell.

In the very unlikely case that only a different OS or Go version broke
the long tests in a CL, the entire matrix will enable them when testing
the default branch once the CL is merged.

Signed-off-by: Daniel Martí <mvdan@mvdan.cc>
Change-Id: Ia88f26439aea324f9d229b170e58e85136210641
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/551229
Reviewed-by: Paul Jolly <paul@myitcv.io>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>

.github/workflows/trybot.yml

@@ -69,7 +69,7 @@ jobs:
           		exit 1
           	fi
           done
-      - if: (github.ref == 'refs/heads/master' || startsWith(github.ref, 'refs/heads/release-branch.'))
+      - if: (github.ref == 'refs/heads/master' || startsWith(github.ref, 'refs/heads/release-branch.')) || (matrix.go-version == '1.19.x' && matrix.os == 'ubuntu-20.04')
         run: echo CUE_LONG=true >> $GITHUB_ENV
       - if: (matrix.go-version == '1.19.x' && matrix.os == 'ubuntu-20.04')
         name: Generate

internal/ci/github/trybot.cue

@@ -69,7 +69,7 @@ trybot: _base.#bashWorkflow & {
 					if: _#isLatestLinux
 				},
 				json.#step & {
-					if:  _#isProtectedBranch
+					if: "\(_#isProtectedBranch) || \(_#isLatestLinux)"
 					run: "echo CUE_LONG=true >> $GITHUB_ENV"
 				},
 				_#goGenerate,