Function createLegacyOutput

packages/plugin-legacy/src/index.ts:450–460

(
        options: Rollup.OutputOptions = {},
      )

      }

      const createLegacyOutput = (
        options: Rollup.OutputOptions = {},
      ): Rollup.OutputOptions => {
        return {
          ...options,
          format: 'esm',
          entryFileNames: getLegacyOutputFileName(options.entryFileNames),
          chunkFileNames: getLegacyOutputFileName(options.chunkFileNames),
          minify: false, // minify with terser instead
        }
      }

      const { rolldownOptions } = config.build
      const { output } = rolldownOptions