fix(compiler-sfc): fix style injection when using normal script + setup

fix #3688

packages/compiler-sfc/__tests__/__snapshots__/cssVars.spec.ts.snap

@@ -109,3 +109,26 @@ return { color, size, ref }
 
 }"
 `;
+
+exports[`CSS vars injection w/ normal <script> binding analysis 1`] = `
+"
+      const __default__ = {
+        setup() {
+          return {
+            size: ref('100px')
+          }
+        }
+      }
+      
+import { useCssVars as _useCssVars } from 'vue'
+const __injectCSSVars__ = () => {
+_useCssVars(_ctx => ({
+  \\"xxxxxxxx-size\\": (_ctx.size)
+}))}
+const __setup__ = __default__.setup
+__default__.setup = __setup__
+  ? (props, ctx) => { __injectCSSVars__();return __setup__(props, ctx) }
+  : __injectCSSVars__
+
+export default __default__"
+`;