Merge pull request #1363 from OfficeDev/huajie/hotfix-oa-tab

fix(hotfix): outlook add-in and tab postbuild script

hello-world-teams-tab-and-outlook-add-in/package.json

@@ -9,7 +9,7 @@
     "build:tab": "cd tab && npm run build",
     "build:add-in": "cd add-in && npm run build",
     "build": "npm run build:tab && npm run build:add-in",
-    "postbuild": "ncp tab/dist build && ncp add-in/dist build",
+    "postbuild": "npx ncp tab/dist build && ncp add-in/dist build",
     "dev:teamsfx": "env-cmd --silent -f .localConfigs npm run start:tab",
     "install": "npm run install:add-in && npm run install:tab",
     "install:add-in": "cd add-in && npm install",