make build failed (newbie question)

[Didier Wiroth <didier_(_dot_)_wiroth_(_at_)_mcesr_(_dot_)_etat_(_dot_)_lu>]

Hi,
(I'm a bsd novice)

I'm experimenting with openbsd. I've been using 3.6 for a few month now.

I have a first question:
As Openbsd 3.7 has not been released yet, but the the OPENBSD_3_7_BASE
cvs tag has been fixed.
For now, and until the release date of 3.7 Is OPENBSD_3_7_BASE = CURRENT

3.7 being around the corner, I decided to upgrade to the latest binary
snapshot.
Being curious, I wanted even more and decided to updated my sources to
OPENBSD_3_7_BASE to do a "make build".

I followed the FAQ:
1) upgraded my 3.6 to the latest snapshot (from 3rd April,
ftp.belnet.be)
2) updated my /etc
3) as mentionned above (update my sources with cvsup to
OPENBSD_3_7_BASE)
4) make build

Unfortunately make build fails, here is the output:
----START OUTPUT-----
===> usr.sbin/httpd
rm -f src/support/dbmmanage.cat1 src/support/htdigest.cat1
src/support/htpasswd.cat1 src/support/apachectl.cat8
src/support/logresolve.cat8 httpd.cat8 src/support/rotatelogs.cat8
src/support/apxs.cat8 src/support/suexec.cat8 src/support/dbmmanage.ps1
src/support/htdigest.ps1 src/support/htpasswd.ps1
src/support/apachectl.ps8 src/support/logresolve.ps8 httpd.ps8
src/support/rotatelogs.ps8 src/support/apxs.ps8 src/support/suexec.ps8
make: don't know how to make clean. Stop in /usr/src/usr.sbin/httpd.
*** Error code 2

Stop in /usr/src/usr.sbin/httpd (line 888 of Makefile.bsd-wrapper).
*** Error code 1

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

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

Stop in /usr/src (line 72 of Makefile).
----END OUTPUT-----

Did I do something wrong? I really would like to know why it can't
build?
Could someone explain and/or give me the solution on how to successfully
build the system?

Many thx
Didier