WITH_LIBCPLUSPLUS on FreeBSD 10.0-CURRENT/amd64 fails with CLANG:

When compiling most recent CURRENT on amd64 platform, using CLANG and
enabled WITH_LIBCPLUSPLUS, I receive the follwing error since two days
now. Build shown below was made avoiding -jX when doing buildworld.

[SNIP]
rpcgen -C -c /usr/src/lib/librpcsvc/../../include/rpcsvc/ypupdate_prot.x
-o ypupdate_prot_xdr.c
rm -f .depend
CC='cc -m32 -march=native -DCOMPAT_32BIT  -isystem
/usr/obj/usr/src/lib32/usr/include/  -L/usr/obj/usr/src/lib32/usr/lib32
 -B/usr/obj/usr/src/lib32/usr/lib32' mkdep -f .depend -a    -DYP
-I/usr/obj/usr/src/lib32/usr/include/rpcsvc -std=gnu99  klm_prot_xdr.c
mount_xdr.c nfs_prot_xdr.c nlm_prot_xdr.c rex_xdr.c rnusers_xdr.c
rquota_xdr.c rstat_xdr.c rwall_xdr.c sm_inter_xdr.c spray_xdr.c
yppasswd_xdr.c ypxfrd_xdr.c ypupdate_prot_xdr.c
/usr/src/lib/librpcsvc/rnusers.c /usr/src/lib/librpcsvc/rstat.c
/usr/src/lib/librpcsvc/rwall.c /usr/src/lib/librpcsvc/yp_passwd.c
/usr/src/lib/librpcsvc/yp_update.c /usr/src/lib/librpcsvc/secretkey.c
/usr/src/lib/librpcsvc/xcrypt.c
===> lib/libsbuf (depend)
===> lib/libtacplus (depend)
===> lib/libutil (depend)
===> lib/libypclnt (depend)
===> lib/libcxxrt (depend)
===> lib/libc++ (depend)
rm -f .depend
CC='cc -m32 -march=native -DCOMPAT_32BIT  -isystem
/usr/obj/usr/src/lib32/usr/include/  -L/usr/obj/usr/src/lib32/usr/lib32
 -B/usr/obj/usr/src/lib32/usr/lib32' mkdep -f .depend -a
-I/usr/src/lib/libc++/../../contrib/libc++/include
-I/usr/src/lib/libc++/../../contrib/libcxxrt -DLIBCXXRT -std=c++0x
/usr/src/lib/libc++/../../contrib/libc++/src/algorithm.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/bind.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/chrono.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/condition_variable.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/debug.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/exception.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/future.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/hash.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/ios.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/iostream.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/locale.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/memory.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/mutex.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/new.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/random.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/regex.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/stdexcept.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/string.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/strstream.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/system_error.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/thread.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/typeinfo.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/utility.cpp
/usr/src/lib/libc++/../../contrib/libc++/src/valarray.cpp
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
cc1plus: error: unrecognized command line option "-std=c++0x"
mkdep: compile failed