I have the same problem, but even after downloading the jdk- 8u101 from Oracle, and directing the Environment Variable JAVA_HOME to it, it still says "Build Failed!"
Execution failed for task ':makeStart'.
> 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_91"