optim: only check types once (#758)

- each format has the same input, so type-checking only needs to
  occur once total
  - previously it was once per format

Change-Id: I998648be8181371ec14e23a3096dc3b4ac731957

Co-authored-by: Lai Hongjie <laihongjie@bytedance.com>

Author: Semesse

src/createRollupConfig.ts

@@ -176,7 +176,7 @@ export async function createRollupConfig(
               : {}),
           },
         },
-        check: !opts.transpileOnly,
+        check: !opts.transpileOnly && outputNum === 0,
         useTsconfigDeclarationDir: Boolean(tsCompilerOptions?.declarationDir),
       }),
       babelPluginTsdx({