e7223eeffb
1. Avoid a cd back into ${.CURDIR} to run mkbuiltins when we know make will first cd into ${.OBJDIR}. Keep the cwd to what make sets it to. 2. Don't tell mkbuiltins where to write to (= ${.OBJDIR}), but where to get sources from (= ${.CURDIR}). This to compensate for point 1. This fixes a problem with bmake's mk files that optimize ${.OBJDIR} to expand to "." after changing cwd, not taking into account that the target is pretty much undoing that and not getting the full path to the object tree anymore.