fix: ensure dynamic publicPath is set early in lib/wc mode

fix #1253

packages/@vue/cli-service/lib/commands/build/entry-lib.js

@@ -1,14 +1,4 @@
-;(function () {
-  if (typeof window !== 'undefined') {
-    let i
-    if ((i = window.document.currentScript) && (i = i.src.match(/(.+\/)[^/]+\.js$/))) {
-      __webpack_public_path__ = i[1] // eslint-disable-line
-    }
-  } else {
-    __webpack_public_path__ = '/' // eslint-disable-line
-  }
-})()
-
+import './setPublicPath'
 import mod from '~entry'
 export default mod
 export * from '~entry'

packages/@vue/cli-service/lib/commands/build/resolveWcEntry.js

@@ -46,6 +46,7 @@ exports.resolveEntry = (prefix, libName, files, async) => {
       : files.map(file => createElement(prefix, file, file, async)).join('\n')
 
   const content = `
+import './setPubicPath'
 import Vue from 'vue'
 import wrap from '@vue/web-component-wrapper'
 
@@ -54,13 +55,6 @@ import 'css-loader/lib/css-base'
 import 'vue-style-loader/lib/addStylesShadow'
 import 'vue-loader/lib/runtime/componentNormalizer'
 
-;(() => {
-  let i
-  if ((i = document.currentScript) && (i = i.src.match(/(.+\\/)[^/]+\\.js$/))) {
-    __webpack_public_path__ = i[1]
-  }
-})()
-
 ${elements}`.trim()
   fs.writeFileSync(filePath, content)
   return filePath

packages/@vue/cli-service/lib/commands/build/setPublicPath.js

@@ -0,0 +1,8 @@
+// This file is imported into lib/wc client bundles.
+
+if (typeof window !== 'undefined') {
+  let i
+  if ((i = window.document.currentScript) && (i = i.src.match(/(.+\/)[^/]+\.js$/))) {
+    __webpack_public_path__ = i[1] // eslint-disable-line
+  }
+}