Force gradle to Java 8 until internal issues are resolved

build.gradle

@@ -62,6 +62,10 @@ idea {
     }
 }
 
+if(JavaVersion.current() != JavaVersion.VERSION_1_8) {
+    throw new GradleException("This project requires Java 8, but it's running on " + JavaVersion.current())
+}
+
 checkPropertyExists("modName")
 checkPropertyExists("modId")
 checkPropertyExists("modGroup")