直接用最新版本的cocos打包apk，都是按照一键安装下载的东西，执行时报了以下错误，是什么原因：
BUILD FAILED
D:\sdk\Android-SDK\tools\ant\build.xml:720: The following error occurred while executing this line:
D:\sdk\Android-SDK\tools\ant\build.xml:734: Unable to find a javac compiler;
com.sun.tools.javac.Main is not on the classpath.
Perhaps JAVA_HOME does not point to the JDK.
It is currently set to “C:\Program Files\Java\jre1.8.0_45”
我的环境变量JAVA_HOME:C:\Program Files\Java\jre1.8.0_45\
