Error in 'make buildworld' on 10.3

[Aijaz Baig]

I am trying to buildworld on 10.3 and I encounter an error:

--- _worldtmp ---
--------------------------------------------------------------
>>> Rebuilding the temporary build tree
--------------------------------------------------------------
rm -rf /mnt/ObjDir/usr/src/tmp
rm -rf /mnt/ObjDir/usr/src/lib32
mkdir -p /mnt/ObjDir/usr/src/tmp/lib
mkdir -p /mnt/ObjDir/usr/src/tmp/usr
mkdir -p /mnt/ObjDir/usr/src/tmp/legacy/bin
mkdir -p /mnt/ObjDir/usr/src/tmp/legacy/usr
mtree -deU -f /usr/src/etc/mtree/BSD.usr.dist  -p
/mnt/ObjDir/usr/src/tmp/legacy/usr >/dev/null
mtree -deU -f /usr/src/etc/mtree/BSD.groff.dist  -p
/mnt/ObjDir/usr/src/tmp/legacy/usr >/dev/null
mtree -deU -f /usr/src/etc/mtree/BSD.usr.dist  -p
/mnt/ObjDir/usr/src/tmp/usr >/dev/null
mtree -deU -f /usr/src/etc/mtree/BSD.include.dist  -p
/mnt/ObjDir/usr/src/tmp/usr/include >/dev/null
ln -sf /usr/src/sys /mnt/ObjDir/usr/src/tmp
--- _legacy ---
--------------------------------------------------------------
>>> stage 1.1: legacy release compatibility shims
--------------------------------------------------------------
cd /usr/src; MAKEOBJDIRPREFIX=/mnt/ObjDir/usr/src/tmp  INSTALL="sh
/usr/src/tools/install.sh"
 PATH=/mnt/ObjDir/usr/src/tmp/legacy/usr/sbin:/mnt/ObjDir/usr/src/tmp/legacy/usr/bin:/mnt/ObjDir/usr/src/tmp/legacy/usr/games:/mnt/ObjDir/usr/src/tmp/legacy/bin:/sbin:/bin:/usr/sbin:/usr/bin
 WORLDTMP=/mnt/ObjDir/usr/src/tmp  VERSION="FreeBSD 10.3-RELEASE amd64
1003000"  MAKEFLAGS="-m /usr/src/tools/build/mk  -j 4 -J 15,16 -m
/usr/src/share/mk"  COMPILER_TYPE=clang make  -f Makefile.inc1  DESTDIR=
 BOOTSTRAPPING=1003000  SSP_CFLAGS=  -DWITHOUT_HTML -DWITHOUT_INFO
-DNO_LINT -DWITHOUT_MAN  -DNO_PIC -DNO_PROFILE -DNO_SHARED
 _BOOTSTRAP_MAKEINFO=yes  -DNO_CPU_CFLAGS -DNO_WARNS -DNO_CTF -DEARLY_BUILD
-DNO_TESTS legacy
--- legacy ---
===> tools/build (obj,includes,depend,all,install)
--- obj ---
/mnt/ObjDir/usr/src/tmp/usr/src/tools/build created for /usr/src/tools/build
--- includes ---
; cd /usr/src/tools/build; make buildincludes; make installincludes
--- .depend ---
rm -f .depend
mkdep -f .depend -a    -I/mnt/ObjDir/usr/src/tmp/legacy/usr/include
-std=gnu99    /usr/src/tools/build/../../contrib/libc-pwcache/pwcache.c
/usr/src/tools/build/../../contrib/libc-pwcache/pwcache.c:82:10: fatal
error: 'namespace.h' file not found
#include "namespace.h"
         ^
1 error generated.
mkdep: compile failed
*** [.depend] Error code 1

make[3]: stopped in /usr/src/tools/build
1 error

make[3]: stopped in /usr/src/tools/build
*** [legacy] Error code 2

make[2]: stopped in /usr/src
1 error

make[2]: stopped in /usr/src
*** [_legacy] Error code 2

make[1]: stopped in /usr/src
1 error

make[1]: stopped in /usr/src
*** [buildworld] Error code 2

make: stopped in /usr/src
1 error

make: stopped in /usr/src

What is this error? Am I missing certain header files? Keen to hear
-- 

Best Regards,
Aijaz Baig