fix: fix build --dest option (vuejs#6314)

Closes vuejs#6312

packages/@vue/cli-service/__tests__/build.spec.js

@@ -91,6 +91,20 @@ test('build with --report-json', async () => {
   expect(appChunk).toHaveProperty('modules')
 })
 
+test('build with --dest', async () => {
+  const project = await create('e2e-build-dest', defaultPreset)
+
+  const { stdout } = await project.run('vue-cli-service build --dest other_dist')
+  expect(stdout).toMatch('Build complete.')
+
+  expect(project.has('other_dist/index.html')).toBe(true)
+  expect(project.has('other_dist/favicon.ico')).toBe(true)
+  expect(project.has('other_dist/js')).toBe(true)
+  expect(project.has('other_dist/css')).toBe(true)
+
+  expect(project.has('dist')).toBe(false)
+})
+
 afterAll(async () => {
   if (browser) {
     await browser.close()

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

@@ -12,7 +12,7 @@ module.exports = (api, args, options) => {
   // respect inline build destination in copy plugin
   if (args.dest && config.plugins.has('copy')) {
     config.plugin('copy').tap(pluginArgs => {
-      pluginArgs[0][0].to = targetDir
+      pluginArgs[0].patterns.to = targetDir
       return pluginArgs
     })
   }