fix(legacy): don't force set build.target when renderLegacyChunks=false (fixes #10201) (#10220)

Author: sapphi-red

packages/plugin-legacy/src/index.ts

@@ -176,17 +176,19 @@ function viteLegacyPlugin(options: Options = {}): Plugin[] {
           config.build.cssTarget = 'chrome61'
         }
 
-        // Vite's default target browsers are **not** the same.
-        // See https://github.com/vitejs/vite/pull/10052#issuecomment-1242076461
-        overriddenBuildTarget = config.build.target !== undefined
-        // browsers supporting ESM + dynamic import + import.meta
-        config.build.target = [
-          'es2020',
-          'edge79',
-          'firefox67',
-          'chrome64',
-          'safari11.1'
-        ]
+        if (genLegacy) {
+          // Vite's default target browsers are **not** the same.
+          // See https://github.com/vitejs/vite/pull/10052#issuecomment-1242076461
+          overriddenBuildTarget = config.build.target !== undefined
+          // browsers supporting ESM + dynamic import + import.meta
+          config.build.target = [
+            'es2020',
+            'edge79',
+            'firefox67',
+            'chrome64',
+            'safari11.1'
+          ]
+        }
       }
 
       return {