无效的源版本：Gradle build时为1.8

Question

我的build.gradle

中有以下一行

sourceCompatibility = 1.8

当我编译它时，会发生以下错误：

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':compileJava'.
> invalid source release: 1.8

将JAVA_HOME设置为短文件名没有帮助。

如何使用Windows 8下的Java 8构建Gradle？

更新

C:\>echo %JAVA_HOME%
C:\PROGRA~1\Java\jdk1.8.0_91

C:\>dir %JAVA_HOME%
COPYRIGHT  README.html                         THIRDPARTYLICENSEREADME.txt  db       javafx-src.zip  lib      src.zip
LICENSE    THIRDPARTYLICENSEREADME-JAVAFX.txt  bin                          include  jre             release