fix(cli): improve error output (#3263)

Co-authored-by: Paul Moss <paulmoss06@gmail.com>

packages/cli/src/index.ts

@@ -48,11 +48,18 @@ export async function build(_options: CliOptions) {
     }),
   )
 
-  if (!options.stdout) {
-    consola.log(green(`${name} v${version}`))
-    consola.start(`UnoCSS ${options.watch ? 'in watch mode...' : 'for production...'}`)
+  if (options.stdout && options.outFile) {
+    consola.fatal(`Cannot use --stdout and --out-file at the same time`)
+    return
   }
 
+  consola.log(green(`${name} v${version}`))
+
+  if (options.watch)
+    consola.start('UnoCSS in watch mode...')
+  else
+    consola.start('UnoCSS for production...')
+
   const debouncedBuild = debounce(
     async () => {
       generate(options).catch(handleError)
@@ -61,7 +68,7 @@ export async function build(_options: CliOptions) {
   )
 
   const startWatcher = async () => {
-    if (options.stdout || !options.watch)
+    if (!options.watch)
       return
     const { patterns } = options