chore(java): detect sample-secrets in build.sh (#998)

Fixes #904

Author: Neenu1995

synthtool/gcp/templates/java_library/.kokoro/build.sh

@@ -79,6 +79,11 @@ samples)
 
  if [[ -f ${SAMPLES_DIR}/pom.xml ]]
  then
+ for FILE in ${KOKORO_GFILE_DIR}/secret_manager/*-samples-secrets; do
+ [[ -f "$FILE" ]] || continue
+ source "$FILE"
+ done
+
  pushd ${SAMPLES_DIR}
  mvn -B \
  -Penable-samples \