Unfortunately there are two slight problems with that:
- Yacc and lex might generate code that generates warnings because of
this. Require yacc and lex to be rebuilt during bootstrap. I'm not
incrementing __FreeBSD_version here, because I assume someone else
will do this eventually.
- When running `make buildkernel', it uses share/mk from the source
treeo to build aicasm. Because aicasm also depends on lex, this would
break. Lower WARNS to 5 for now. We should just increment it to 6
again somewhere in the very far future.