This changes the buildlink3.mk files to use an include guard for the recursive include. The use of BUILDLINK_DEPTH, BUILDLINK_DEPENDS, BUILDLINK_PACKAGES and BUILDLINK_ORDER is handled by a single new variable BUILDLINK_TREE. Each buildlink3.mk file adds a pair of enter/exit marker, which can be used to reconstruct the tree and to determine first level includes. Avoiding := for large variables (BUILDLINK_ORDER) speeds up parse time as += has linear complexity. The include guard reduces system time by avoiding reading files over and over again. For complex packages this reduces both %user and %sys time to half of the former time.
but in actuality it is 20070625. My poor excuse for the screwup is that it has been sitting in my tree for a while.