Create .gitignore on postBuild (#18045)

ui/lib/keep-gitkeep/index.js

@@ -0,0 +1,15 @@
+'use strict';
+const fs = require('fs');
+module.exports = {
+  name: require('./package').name,
+
+  isDevelopingAddon() {
+    return true;
+  },
+
+  postBuild(result) {
+    // We gitignore the contents of our output directory http/web_ui
+    // but we need to keep the folder structure for the Vault build
+    fs.writeFileSync(result.directory + '/.gitkeep', '');
+  },
+};

ui/lib/keep-gitkeep/package.json

@@ -0,0 +1,6 @@
+{
+  "name": "keep-gitkeep",
+  "keywords": [
+    "ember-addon"
+  ]
+}

ui/package.json

@@ -239,6 +239,7 @@
     "paths": [
       "lib/core",
       "lib/css",
+      "lib/keep-gitkeep",
       "lib/kmip",
       "lib/open-api-explorer",
       "lib/pki",