Update ping/pong demo with bom file

demos/golang/grpc_pingpong/ping.yaml

@@ -0,0 +1,11 @@
+includes:
+  - base.yaml
+targets:
+  - target: /bin
+    copy:
+      - files:
+        - ../occlum_ping
+  - target: /etc
+    copy:
+      - files:
+        - /etc/hosts

demos/golang/grpc_pingpong/pong.yaml

@@ -0,0 +1,11 @@
+includes:
+  - base.yaml
+targets:
+  - target: /bin
+    copy:
+      - files:
+        - ../occlum_pong
+  - target: /etc
+    copy:
+      - files:
+        - /etc/hosts

demos/golang/grpc_pingpong/run_ping_on_occlum.sh

@@ -25,8 +25,8 @@ new_json="$(jq '.resource_limits.user_space_size = "2560MB" |
 echo "${new_json}" > Occlum.json
 
 # 2. Copy program into Occlum Workspace and build
-cp ../occlum_ping image/bin
-cp /etc/hosts image/etc/
+rm -rf image && \
+copy_bom -f ../ping.yaml --root image --include-dir /opt/occlum/etc/template && \
 occlum build
 
 # 3. Run the hello world sample

demos/golang/grpc_pingpong/run_pong_on_occlum.sh

@@ -25,8 +25,8 @@ new_json="$(jq '.resource_limits.user_space_size = "2560MB" |
 echo "${new_json}" > Occlum.json
 
 # 2. Copy program into Occlum Workspace and build
-cp ../occlum_pong image/bin
-cp /etc/hosts image/etc/
+rm -rf image && \
+copy_bom -f ../pong.yaml --root image --include-dir /opt/occlum/etc/template && \
 occlum build
 
 # 3. Run the hello world sample