ReflectionHelper cannot resolve CraftEntity on Mac and Linux

[jwulf]

On Mac and Linux:

[08:13:41 INFO]: [ReflectionHelper] Generating dynamic constant...
[08:13:41 INFO]: [ReflectionHelper] Version is UNKNOWN (-1)
[08:13:41 ERROR]: Could not load 'plugins/BossBarAPI_v2.4.1.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.ExceptionInInitializerError
...
Caused by: java.lang.RuntimeException: java.lang.ClassNotFoundException: Could not resolve class for [ResolverQuery{name='org.bukkit.craftbukkit.UNKNOWN.entity.CraftEntity', types=[]}]
...
Caused by: java.lang.ClassNotFoundException: Could not resolve class for [ResolverQuery{name='org.bukkit.craftbukkit.UNKNOWN.entity.CraftEntity', types=[]}]

[jwulf]

Further information:

[01:11:35 INFO]: This server is running CraftBukkit version git-Spigot-65a0347-1a71021 (MC: 1.11.2) (Implementing API version 1.11.2-R0.1-SNAPSHOT)

java -version
java version "1.8.0_73"
Java(TM) SE Runtime Environment (build 1.8.0_73-b02)
Java HotSpot(TM) 64-Bit Server VM (build 25.73-b02, mixed mode)

[jwulf]

I'm submitting another pull request with a patch that works from load to run-time usage.