you must buildworld before you buildkernel. why ?

[Saifi Khan]

Hi:

i'm trying to compile a custom kernel on my AMD64 X2 box, and in
encouter the notification shown below.

"""
# make buildkernel KERNCONF=SYNERGY
You must buildworld before buildkernel.  If you wish
to build a kernel using native tools, config it manually
or use the nativekernel target if you are in a rush
*** Error code 1

Stop in /usr/src.
*** Error code 1

Stop in /usr/src.
# 
"""

As i'm a newbie, can some of the more experienced folks share
the reason for the requirement to 'buildworld' before
'buildkernel' ?

Additionally, there doesn't seem to be this requirement when
compiling a custom kernel on FreeBSD. Any pointers ?

Thanks in advance.


thanks
Saifi.