Update cluster serving demo with copy_bom

demos/cluster_serving/cluster_serving.yaml

@@ -0,0 +1,23 @@
+includes: 
+  - base.yaml
+  - java-11-openjdk-amd64.yaml
+targets: 
+  # copy flink
+  - target: /bin
+    copy:
+      - from: ../flink-${FLINK_VERSION}
+  - target: /opt
+    copy:
+      - dirs:
+        - ../flink-${FLINK_VERSION}/conf
+  # copy hosts and localtime
+  - target: /etc
+    copy: 
+      - files: 
+          - ../hosts
+          - /etc/localtime
+  # copy libnss_files
+  - target: /opt/occlum/glibc/lib
+    copy: 
+      - files: 
+          - /opt/occlum/glibc/lib/libnss_files.so.2

demos/cluster_serving/init-occlum-taskmanager.sh

@@ -21,17 +21,8 @@ init_instance() {
 
 build_flink() {
     # Copy JVM and class file into Occlum instance and build
-    mkdir -p image/usr/lib/jvm
-    cp -r /usr/lib/jvm/java-11-openjdk-amd64 image/usr/lib/jvm
-    cp /lib/x86_64-linux-gnu/libz.so.1 image/lib
-    cp $occlum_glibc/libdl.so.2 image/$occlum_glibc
-    cp $occlum_glibc/librt.so.1 image/$occlum_glibc
-    cp $occlum_glibc/libm.so.6 image/$occlum_glibc
-    cp $occlum_glibc/libnss_files.so.2 image/$occlum_glibc
-    cp -rf ../flink-${FLINK_VERSION}/* image/bin/
-    cp -rf ../flink-${FLINK_VERSION}/conf image/opt/
-    cp -rf /etc/java-11-openjdk image/etc/
-    cp -rf ../hosts image/etc/
+    rm -rf image
+    copy_bom -f ../cluster_serving.yaml --root image --include-dir /opt/occlum/etc/template
     # build occlum
     occlum build
 }