DTRACE build failure (/usr/obj/usr/src/tmp/usr/bin/ld: cannot find -lpthread)

Hi,

im trying to build an dtrace enabled FreeBSD current and use the source
from:
*default host=cvsup10.freebsd.org 
*default release=cvs
*default delete use-rel-suffix
p4-cvs-dtraced

Details at: http://people.freebsd.org/~jb/dtrace/

Unfortunally I am not able to finish the build because it always breaks
in /usr/src/cddl/usr.bin/ctfconvert with this ld-error:
/usr/obj/usr/src/tmp/usr/bin/ld: cannot find -lpthread

I was able to "solve" this problem by adding the following line to the Makefile:
CFLAGS += -L/usr/obj/usr/src/lib/libpthread

But now it hangs in ggatec:

===> sbin/ggate (all)
===> sbin/ggate/ggatec (all)
cc -O2 -fno-strict-aliasing -pipe -DNO_MALLOC_EXTRAS -O -pipe  -DLIBGEOM 
-I/usr/src/sbin/ggate/ggat ec/../shared -g -Wsystem-headers -Werror -Wall 
-Wno-format-y2k -W -Wno-unused-parameter -Wstrict-pr ototypes
 -Wmissing-prototypes -Wpointer-arith -Wreturn-type -Wcast-qual 
-Wwrite-strings -Wswitch -W shadow -Wcast-align -Wunused-parameter 
-Wchar-subscripts -Winline -Wnested-externs -Wredundant-decl s -c
 /usr/src/sbin/ggate/ggatec/ggatec.c
ctfconvert -L VERSION ggatec.o
cc -O2 -fno-strict-aliasing -pipe -DNO_MALLOC_EXTRAS -O 
-pipe  -DLIBGEOM -I/usr/src/sbin/ggate/ggat ec/../shared -g 
-Wsystem-headers -Werror -Wall -Wno-format-y2k -W -Wno-unused-parameter
 -Wstrict-pr ototypes -Wmissing-prototypes -Wpointer-arith -Wreturn-type
 -Wcast-qual -Wwrite-strings -Wswitch -W shadow -Wcast-align -Wunused-parameter
 -Wchar-subscripts -Winline -Wnested-externs -Wredundant-decl s -c
 /usr/src/sbin/ggate/ggatec/../shared/ggate.c
ctfconvert -L VERSION ggate.o
cc -O2 -fno-strict-aliasing -pipe -DNO_MALLOC_EXTRAS -O -pipe  -DLIBGEOM 
-I/usr/src/sbin/ggate/ggat ec/../shared -g -Wsystem-headers -Werror
 -Wall -Wno-format-y2k -W -Wno-unused-parameter -Wstrict-pr ototypes
 -Wmissing-prototypes -Wpointer-arith -Wreturn-type -Wcast-qual -Wwrite-strings 
-Wswitch -W shadow -Wcast-align -Wunused-parameter -Wchar-subscripts -Winline 
-Wnested-externs -Wredundant-decl s  -o ggatec ggatec.o ggate.o -lgeom -lsbuf 
-lbsdxml -lutil -lpthread
/usr/obj/usr/src/tmp/usr/bin/ld: cannot find -lpthread
*** Error code 1

Stop in /usr/src/sbin

Is there something generally broken with my threading libraries? It doesn't seem to be an dtrace issue?

Thanks for any hint to solve this problem.

Tobias