[fix](compile) auto-regenerate hadoop-deps/lib when missing due to Ma… (#60964)

…ven cache

Problem:
- When Maven build cache is hit, the dependency:copy-dependencies plugin
  execution is skipped
- This causes target/lib directory to be missing in hadoop-deps module
- Results in an incomplete BE output package without Hadoop dependencies

Solution:
- Add automatic regeneration logic in build.sh copy phase
- When lib directory is missing and BUILD_BE_JAVA_EXTENSIONS=1,
  execute 'mvn dependency:copy-dependencies' to regenerate it
- Preserves Maven cache benefits while ensuring complete output

Impact:
- Fixes intermittent missing hadoop_hdfs jars in BE output
- No impact on normal build flow (only triggers when needed)
- Maintains build cache acceleration for other plugins

Related PR: #60819

Author: hello-stephen

build.sh

@@ -970,6 +970,13 @@ EOF
             mkdir "${BE_HADOOP_HDFS_DIR}"
             HADOOP_DEPS_JAR_DIR="${DORIS_HOME}/fe/be-java-extensions/${HADOOP_DEPS_NAME}/target"
             echo "HADOOP_DEPS_JAR_DIR: ${HADOOP_DEPS_JAR_DIR}"
+            if  [[ "${BUILD_BE_JAVA_EXTENSIONS}" -eq 1 && ! -d "${HADOOP_DEPS_JAR_DIR}/lib" ]]; then
+                echo "WARN: lib directory missing (likely due to Maven cache). Regenerating..."
+                pushd "${DORIS_HOME}/fe/be-java-extensions/${HADOOP_DEPS_NAME}"
+                "${MVN_CMD}" dependency:copy-dependencies -DskipTests -Dcheckstyle.skip=true
+                mv target/dependency target/lib
+                popd
+            fi
             if [[ -f "${HADOOP_DEPS_JAR_DIR}/${HADOOP_DEPS_NAME}.jar" ]]; then
                 echo "Copy Be Extensions hadoop deps jar to ${BE_HADOOP_HDFS_DIR}"
                 cp "${HADOOP_DEPS_JAR_DIR}/${HADOOP_DEPS_NAME}.jar" "${BE_HADOOP_HDFS_DIR}"