fix debug mode check on windows

packages/@vue/cli/bin/vue

@@ -2,6 +2,7 @@
 
 const fs = require('fs')
 const path = require('path')
+const slash = require('slash')
 const chalk = require('chalk')
 const semver = require('semver')
 const { error } = require('@vue/cli-shared-utils')
@@ -16,7 +17,7 @@ if (!semver.satisfies(process.version, requiredVersion)) {
 }
 
 // enter debug mode when creating test repo
-if (process.cwd().indexOf('/packages/test') > 0 &&
+if (slash(process.cwd()).indexOf('/packages/test') > 0 &&
     fs.existsSync(path.resolve(process.cwd(), '../@vue'))) {
   process.env.VUE_CLI_DEBUG = true
 }