smoketest: don't run the pre-push hook when pushing to the VM

upstream_set pushes the commit under test from the working copy, so
coredesktop-dev's pre-push hook ran make check on every push to the VM.
Inside the smoketest those checks saw VM_GIT_URL and friends, the
smoketest tests pushed to the real VM and failed, and the hook stopped
the push, failing the installed image's build. The push now uses
--no-verify, and the tests clear the smoketest's variables.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

smoketest/lib/scenario.sh

@@ -99,7 +99,9 @@ upstream_set() {
   local sha
   sha="$(git -C "$SMOKETEST_REPO" rev-parse --verify --quiet "$1^{commit}")" \
     || fail "no such commit: $1"
-  GIT_SSH_COMMAND="${VM_GIT_SSH:-ssh}" git -C "$SMOKETEST_REPO" push --quiet --force \
+  # --no-verify: a pre-push hook in the working copy (coredesktop-dev's runs
+  # make check) is for pushes to the real upstream, not to the VM
+  GIT_SSH_COMMAND="${VM_GIT_SSH:-ssh}" git -C "$SMOKETEST_REPO" push --quiet --force --no-verify \
     "${VM_GIT_URL:-}$UPSTREAM" "$sha:refs/heads/main" || fail "couldn't push $1 to the VM"
 }