Only add the spotbugs dependency when jdk8 is active

[INFO] Fork Value is true
     [java] Exception in thread "main" java.lang.UnsupportedClassVersionError: edu/umd/cs/findbugs/FindBugs2 : Unsupported major.minor version 52.0
     [java] 	at java.lang.ClassLoader.defineClass1(Native Method)
     [java] 	at java.lang.ClassLoader.defineClass(ClassLoader.java:803)
     [java] 	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
     [java] 	at java.net.URLClassLoader.defineClass(URLClassLoader.java:442)
     [java] 	at java.net.URLClassLoader.access$100(URLClassLoader.java:64)
     [java] 	at java.net.URLClassLoader$1.run(URLClassLoader.java:354)
     [java] 	at java.net.URLClassLoader$1.run(URLClassLoader.java:348)
     [java] 	at java.security.AccessController.doPrivileged(Native Method)
     [java] 	at java.net.URLClassLoader.findClass(URLClassLoader.java:347)
     [java] 	at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
     [java] 	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:312)
     [java] 	at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
     [java] 	at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:482)