Won't build, period.

Tried different gradle versions, java versions, even tried on a VM. This is the output:

```
* What went wrong:
Execution failed for task ':compileKotlin'.
> Could not resolve all files for configuration ':compileClasspath'.
   > Could not find net.minecraftforge:forge:1.12.2-14.23.5.2855_mapped_stable_39-1.12.
```

Could you include a prebuilt .jar file?