VBox upgrade fails

[AN]

Trying to update VBox fails with:

# portsnap fetch update
Looking up portsnap.FreeBSD.org mirrors... 4 mirrors found.
Fetching snapshot tag from portsnap5.FreeBSD.org... done.
Ports tree hasn't changed since last snapshot.
No updates needed.
Ports tree is already up to date.

# pkg_version -vl\<
virtualbox-ose-4.1.8                <   needs updating (port has 4.1.12)
virtualbox-ose-kmod-4.1.8_1         <   needs updating (port has 4.1.12)

portupgrade -va
--->  Session started at: Tue, 17 Apr 2012 19:58:37 -0400
** Port directory not found: www/FF
--->  Upgrade of emulators/virtualbox-ose-kmod started at: Tue, 17 Apr 
2012 19:59:29 -0400
--->  Upgrading 'virtualbox-ose-kmod-4.1.8_1' to 
'virtualbox-ose-kmod-4.1.12' (emulators/virtualbox-ose-kmod)
--->  Build of emulators/virtualbox-ose-kmod started at: Tue, 17 Apr 2012 
19:59:29 -0400
--->  Building '/usr/ports/emulators/virtualbox-ose-kmod'
===>  Cleaning for dev86-0.16.17
===>  Cleaning for virtualbox-ose-kmod-4.1.12
===>  License GPLv2 accepted by the user
===>  Found saved configuration for virtualbox-ose-kmod-4.1.8_2
===>  Extracting for virtualbox-ose-kmod-4.1.12
=> SHA256 Checksum OK for VirtualBox-4.1.12.tar.bz2.

<snip>

kBuild: Installing 
/usr/ports/emulators/virtualbox-ose-kmod/work/VirtualBox-4.1.12/out/freebsd.amd64/release/bin/src/vboxnetadp/VBoxNetAdpInternal.h
kBuild: Installing 
/usr/ports/emulators/virtualbox-ose-kmod/work/VirtualBox-4.1.12/out/freebsd.amd64/release/bin/src/vboxnetadp/r0drv/freebsd/the-freebsd-kernel.h
kBuild: Installing 
/usr/ports/emulators/virtualbox-ose-kmod/work/VirtualBox-4.1.12/out/freebsd.amd64/release/bin/src/vboxnetadp/version-generated.h
kBuild: Installing 
/usr/ports/emulators/virtualbox-ose-kmod/work/VirtualBox-4.1.12/out/freebsd.amd64/release/bin/src/vboxnetadp/product-generated.h
kBuild: Installing 
/usr/ports/emulators/virtualbox-ose-kmod/work/VirtualBox-4.1.12/out/freebsd.amd64/release/bin/src/vboxnetadp/Makefile
kBuild: Installing 
/usr/ports/emulators/virtualbox-ose-kmod/work/VirtualBox-4.1.12/out/freebsd.amd64/release/bin/src/vboxnetflt/Makefile
cd 
/usr/ports/emulators/virtualbox-ose-kmod/work/VirtualBox-4.1.12/out/freebsd.amd64/release/bin/src 
&& make SYSDIR=/usr/src/sys
*** Building 'vboxdrv' module ***
"/usr/share/mk/bsd.own.mk", line 483: MK_CLANG_IS_CC can't be set by a 
user.
*** [all] Error code 1

Stop in 
/usr/ports/emulators/virtualbox-ose-kmod/work/VirtualBox-4.1.12/out/freebsd.amd64/release/bin/src.
*** [do-build] Error code 1

Stop in /usr/ports/emulators/virtualbox-ose-kmod.
*** [build] Error code 1

Stop in /usr/ports/emulators/virtualbox-ose-kmod.