Freebsd 4.7 to 5.1 buildworld failed!

Hello,

I did a cvsup and retrieved tag=RELENG_5_1_0_RELEASE. Then try to
buildworld and got this error.

:/usr/src# make buildworld
Running test variables
PASS: Test variables detected no regression, output matches.
Running test targets
PASS: Test targets detected no regression.
Running test sysvmatch
PASS: Test sysvmatch detected no regression.
Running test lhs_expn
FAIL: Test failed: regression detected.  See above.
*** Error code 1

Stop in /usr/src/tools/regression/usr.bin/make.
*** Error code 1

Stop in /usr/src/tools/regression/usr.bin/make.

--------------------------------------------------------------
 Building an up-to-date make(1)
--------------------------------------------------------------
rm -f .depend
mkdep -f .depend -a    -I/usr/src/usr.bin/make
-DMAKE_VERSION=\"5200209170\" -D__FBSDID=__RCSID -DDEFSHELL=1
/usr/src/usr.bin/make/arch.c /usr/src/usr.bin/make/buf.c
/usr/src/usr.bin/make/compat.c /usr/src/usr.bin/make/cond.c
/usr/src/usr.bin/make/dir.c /usr/src/usr.bin/make/for.c
/usr/src/usr.bin/make/hash.c /usr/src/usr.bin/make/job.c
/usr/src/usr.bin/make/main.c /usr/src/usr.bin/make/make.c
/usr/src/usr.bin/make/parse.c /usr/src/usr.bin/make/str.c
/usr/src/usr.bin/make/suff.c /usr/src/usr.bin/make/targ.c
/usr/src/usr.bin/make/util.c /usr/src/usr.bin/make/var.c
/usr/src/usr.bin/make/var_modify.c
/usr/src/usr.bin/make/lst.lib/lstAppend.c
/usr/src/usr.bin/make/lst.lib/lstAtEnd.c
/usr/src/usr.bin/make/lst.lib/lstAtFront.c
/usr/src/usr.bin/make/lst.lib/lstClose.c
/usr/src/usr.bin/make/lst.lib/lstConcat.c
/usr/src/usr.bin/make/lst.lib/lstDatum.c
/usr/src/usr.bin/make/lst.lib/lstDeQueue.c
/usr/src/usr.bin/make/lst.lib/lstDestroy.c
/usr/src/usr.bin/make/lst.lib/lstDupl.c
/usr/src/usr.bin/make/lst.lib/lstEnQueue.c
/usr/src/usr.bin/make/lst.lib/lstFind.c
/usr/src/usr.bin/make/lst.lib/lstFindFrom.c
/usr/src/usr.bin/make/lst.lib/lstFirst.c
/usr/src/usr.bin/make/lst.lib/lstForEach.c
/usr/src/usr.bin/make/lst.lib/lstForEachFrom.c
/usr/src/usr.bin/make/lst.lib/lstInit.c
/usr/src/usr.bin/make/lst.lib/lstInsert.c
/usr/src/usr.bin/make/lst.lib/lstIsAtEnd.c
/usr/src/usr.bin/make/lst.lib/lstIsEmpty.c
/usr/src/usr.bin/make/lst.lib/lstLast.c
/usr/src/usr.bin/make/lst.lib/lstMember.c
/usr/src/usr.bin/make/lst.lib/lstNext.c
/usr/src/usr.bin/make/lst.lib/lstOpen.c
/usr/src/usr.bin/make/lst.lib/lstRemove.c
/usr/src/usr.bin/make/lst.lib/lstReplace.c
/usr/src/usr.bin/make/lst.lib/lstSucc.c
In file included from /usr/src/usr.bin/make/cond.c:55:
/usr/include/math.h:20: sys/_types.h: No such file or directory
mkdep: compile failed
*** Error code 1

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

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

Stop in /usr/src.

....

At first I was getting the libpthread error everyone seems to be getting
but now I got this error(after i removed /usr/src and /usr/obj, and cvsup
using HEAD).  Can someone please point me in the right direction.

Thanks

Alex