Fix JJB expansion of shell parameter syntax

Jenkins Job Builder treats {} as template expansion markers. In the
Bazel major-version check, this interferes with the shell parameter
expansion ${BAZEL_MAJOR:-0} used to provide a default value.

Escape the expression by doubling the braces so JJB preserves it
verbatim in the generated job scripts.

This keeps the Bazel >= 9 conditional working as intended in both
Jenkins shell wrappers.

Change-Id: I310b726c580c1658f585ddc25772d39207d3bc13

jenkins/gerrit-bazel-build.sh

diff --git a/jenkins/gerrit-bazel-build.sh b/jenkins/gerrit-bazel-build.sh
index d461927..af91216 100644
--- a/jenkins/gerrit-bazel-build.sh
+++ b/jenkins/gerrit-bazel-build.sh
@@ -22,7 +22,7 @@
 echo "$BAZEL_VERSION_OUTPUT"
 
 BAZEL_MAJOR=$(echo "$BAZEL_VERSION_OUTPUT" | sed -n 's/^Build label: \([0-9][0-9]*\).*/\1/p')
-if [ "${BAZEL_MAJOR:-0}" -ge 9 ]; then
+if [ "${{BAZEL_MAJOR:-0}}" -ge 9 ]; then
   echo "Skipping bazel sync for Bazel $BAZEL_MAJOR"
 else
   echo "Running bazel sync for Bazel $BAZEL_MAJOR"

jenkins/gerrit-mvn-build-plugin.sh

diff --git a/jenkins/gerrit-mvn-build-plugin.sh b/jenkins/gerrit-mvn-build-plugin.sh
index c5468d6..bdde14e 100644
--- a/jenkins/gerrit-mvn-build-plugin.sh
+++ b/jenkins/gerrit-mvn-build-plugin.sh
@@ -20,7 +20,7 @@
 fi
 
 BAZEL_MAJOR=$(echo "$BAZEL_VERSION_OUTPUT" | sed -n 's/^Build label: \([0-9][0-9]*\).*/\1/p')
-if [ "${BAZEL_MAJOR:-0}" -ge 9 ]; then
+if [ "${{BAZEL_MAJOR:-0}}" -ge 9 ]; then
   echo "Skipping bazel sync for Bazel $BAZEL_MAJOR"
 else
   echo "Running bazel sync for Bazel $BAZEL_MAJOR"