Bazel 9 removed the `sync` command, causing CI failures:

  Command 'sync' not found

Run `bazel sync` only for Bazel versions older than 9 by checking the
major version. This keeps the behavior unchanged for older Bazel
versions while allowing CI to work with Bazel 9 and newer.

Change-Id: Ia0490f3ecca3196dc9ed7cc4786dda76f311650d

jenkins/gerrit-bazel-build.sh

diff --git a/jenkins/gerrit-bazel-build.sh b/jenkins/gerrit-bazel-build.sh
index eac1990..d461927 100644
--- a/jenkins/gerrit-bazel-build.sh
+++ b/jenkins/gerrit-bazel-build.sh
@@ -17,12 +17,20 @@
 echo '----------------------------------------------'
 
 java -fullversion
-bazelisk version
 
-# Whilst all the rest of Gerrit is able to automatically sync the Bazel repositories
-# the PolyGerrit part fails to do so when the working directory is replaced with a
-# fresh clone from the remote Git repository
-bazelisk sync --only=npm --only=tools_npm --only=ui_npm --only=plugins_npm
+BAZEL_VERSION_OUTPUT=$(bazelisk version 2>/dev/null)
+echo "$BAZEL_VERSION_OUTPUT"
+
+BAZEL_MAJOR=$(echo "$BAZEL_VERSION_OUTPUT" | sed -n 's/^Build label: \([0-9][0-9]*\).*/\1/p')
+if [ "${BAZEL_MAJOR:-0}" -ge 9 ]; then
+  echo "Skipping bazel sync for Bazel $BAZEL_MAJOR"
+else
+  echo "Running bazel sync for Bazel $BAZEL_MAJOR"
+  # Whilst all the rest of Gerrit is able to automatically sync the Bazel repositories
+  # the PolyGerrit part fails to do so when the working directory is replaced with a
+  # fresh clone from the remote Git repository
+  bazelisk sync --only=npm --only=tools_npm --only=ui_npm --only=plugins_npm
+fi
 
 if [[ "$MODE" == *"rbe"* ]]
 then

jenkins/gerrit-mvn-build-plugin.sh

diff --git a/jenkins/gerrit-mvn-build-plugin.sh b/jenkins/gerrit-mvn-build-plugin.sh
index 7d06ace..c5468d6 100644
--- a/jenkins/gerrit-mvn-build-plugin.sh
+++ b/jenkins/gerrit-mvn-build-plugin.sh
@@ -5,7 +5,9 @@
 git checkout -f -b gerrit-master gerrit/{branch}
 git submodule update --init
 java -fullversion
-bazelisk version
+
+BAZEL_VERSION_OUTPUT=$(bazelisk version 2>/dev/null)
+echo "$BAZEL_VERSION_OUTPUT"
 
 # This is a workaround to Issue 316936462: after the initial build with $BAZEL_OPTS
 # that include a remote cache, the subsequent implicit build commands executed would
@@ -17,10 +19,16 @@
   echo "build $BAZEL_OPTS" >> .bazelrc
 fi
 
-# Whilst all the rest of Gerrit is able to automatically sync the Bazel repositories
-# the PolyGerrit part fails to do so when the working directory is replaced with a
-# fresh clone from the remote Git repository
-bazelisk sync --only=npm --only=tools_npm --only=ui_npm --only=plugins_npm
+BAZEL_MAJOR=$(echo "$BAZEL_VERSION_OUTPUT" | sed -n 's/^Build label: \([0-9][0-9]*\).*/\1/p')
+if [ "${BAZEL_MAJOR:-0}" -ge 9 ]; then
+  echo "Skipping bazel sync for Bazel $BAZEL_MAJOR"
+else
+  echo "Running bazel sync for Bazel $BAZEL_MAJOR"
+  # Whilst all the rest of Gerrit is able to automatically sync the Bazel repositories
+  # the PolyGerrit part fails to do so when the working directory is replaced with a
+  # fresh clone from the remote Git repository
+  bazelisk sync --only=npm --only=tools_npm --only=ui_npm --only=plugins_npm
+fi
 
 bazelisk build api
 ./tools/maven/api.sh install