(New question) BuildTools not compiling when using --rev (version)

I simply need to be able to get the item a player is holding for a 1.8 server running ViaVersion. This is something I haven't done before and didn't have much luck searching for, so I'm not positive if I need to do anything special or what, if this is possible at all.
Thanks in advance <3

 

1.8 is just Player.getInventory()
Wasn't sure, so good to know. Thanks~

 

So, this isn't a problem ^
However, my issue now is that I forgot a small snippet of code cass the player to CraftPlayer, which doesn't seem to work because of the CraftPlayer class varying by version (trying to anyways results in a NoClassDefFoundException or something along those lines). I assumed I might need the other shaded jar files, but BuildTools seemingly won't run if I use --rev <version>..

EDIT://
Seemingly found a solution. Might've just been caused by my Java version (was using Java 10, realized from a thread a few months ago I should be using Java 8).