fix: always write override.style

Author: yyx990803

lib/prepare.js

@@ -46,11 +46,9 @@ if (!Object.assign) Object.assign = require('object-assign')`
   await writeTemp('polyfill.js', polyfillCode)
 
   // 5. handle user override
-  if (options.useDefaultTheme) {
-    const overridePath = path.resolve(sourceDir, '.vuepress/override.styl')
-    const hasUserOverride = fs.existsSync(overridePath)
-    await writeTemp(`override.styl`, hasUserOverride ? `@import(${JSON.stringify(overridePath)})` : ``)
-  }
+  const overridePath = path.resolve(sourceDir, '.vuepress/override.styl')
+  const hasUserOverride = options.useDefaultTheme && fs.existsSync(overridePath)
+  await writeTemp(`override.styl`, hasUserOverride ? `@import(${JSON.stringify(overridePath)})` : ``)
 
   async function writeEnhanceTemp (destName, srcPath, isEnhanceExist) {
     await writeTemp(