Add sample test env variable

Author: cindy-peng

.cloudbuild/samples_build.yaml

@@ -13,11 +13,6 @@ steps:
   ]
 - name: gcr.io/cloud-devrel-public-resources/java8
   entrypoint: pwd
-- name: gcr.io/cloud-devrel-public-resources/java8
-  entrypoint: echo
-  args: [
-    '${JAVA11_HOME}'
-  ]
 - name: gcr.io/cloud-devrel-public-resources/java8
   entrypoint: bash
   args: [
@@ -27,7 +22,7 @@ steps:
   - 'JOB_TYPE=samples'
   - 'GOOGLE_CLOUD_PROJECT=cloud-java-ci-sample'
   - 'KOKORO_GITHUB_PULL_REQUEST_NUMBER=$_PR_NUMBER'
-  - 'SUREFIRE_JVM_OPT=-Djvm=${JAVA11_HOME}/bin/java'
+  - 'SUREFIRE_JVM_OPT=-Djvm=/usr/lib/jvm/java-11-openjdk-amd64/bin/java'
 - name: gcr.io/cloud-devrel-public-resources/java8
   entrypoint: echo
   args: [

.kokoro/build.sh

@@ -82,6 +82,8 @@ graalvm17)
     ;;
 samples)
     SAMPLES_DIR=samples
+    echo "SUREFIRE_JVM_OPT: ${SUREFIRE_JVM_OPT}"
+    echo "Java 11: ${JAVA11_HOME}"
     # only run ITs in snapshot/ on presubmit PRs. run ITs in all 3 samples/ subdirectories otherwise.
     if [[ ! -z ${KOKORO_GITHUB_PULL_REQUEST_NUMBER} ]]
     then