j2objc Build

Have you tried the full j2objc build lately?

I am trying to follow the instructions:
https://developers.google.com/j2objc/guides/building-j2objc

But the last buildable commits are half a year old.

The latest version throws a lot of `not supported in -source 8 errors` right at the start. At the same time, `java.mk` explicitly states `-source 1.8 -target 1.8`. If I change it, more errors are thrown, and so on and on.