JAVA_HOME does not point to the JDK #3
Description
Android studio 要 >= JDK 1.7，升级之后，Cordova run 出错：
/Applications/ADT/sdk/tools/ant/build.xml:601: The following error occurred while executing this line:
/Applications/ADT/sdk/tools/ant/build.xml:720: The following error occurred while executing this line:
/Applications/ADT/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 "/Library/Java/JavaVirtualMachines/jdk1.8.0_31.jdk/Contents/Home/jre"找半天没有找到解决方法，只好将环境变量 JAVA_HOME 先设置回 1.6，参考：
How To Set $JAVA_HOME Environment Variable On Mac OS X
# edit ~/.bash_profile && add or edit
export JAVA_HOME=$(/usr/libexec/java_home -v 1.6)