fix bug of set NIGHTLY_MODE;test=document_fix;test=windows_ci (#41758)

paddle/scripts/paddle_build.bat

@@ -75,7 +75,7 @@ if not defined WITH_UNITY_BUILD set WITH_UNITY_BUILD=OFF
 if not defined INFERENCE_DEMO_INSTALL_DIR set INFERENCE_DEMO_INSTALL_DIR=%cache_dir:\=/%/inference_demo
 if not defined LOG_LEVEL set LOG_LEVEL=normal
 if not defined PRECISION_TEST set PRECISION_TEST=OFF
-if not defined NIGHTLY_MODE set PRECISION_TEST=OFF
+if not defined NIGHTLY_MODE set NIGHTLY_MODE=OFF
 if not defined retry_times set retry_times=1
 if not defined PYTHON_ROOT set PYTHON_ROOT=C:\Python37
 if not defined BUILD_DIR set BUILD_DIR=build