CURRENT: lang/gcc fails to build on CURRENT with error: configure: error: no usable dependency style found

I have one specific FreeBSD 10.0-CURRENT box (FreeBSD 10.0-CURRENT #0
r248061: Fri Mar  8 19:44:30 CET 2013 amd64) which rejects to build
either lang/gcc or lang/gcc46 with the very same error shown below.

The box is compiled with CLANG (buildworld/kernel).

It doesn't matter whether I compile those ports with cc (which referes
to CLANG 3.2) or "USE_GCC=any", which should use the legacy compiler gcc
or the installed lang/gcc (which seems to be outdated). Any attempt ends
up with the very same error as shown below.

This problem is sticky for a while now and I do not know what to do. I
don't dare to delete the package in case the problem is then still
present and I couldn't build the port again (I have to many scientific
packages which do not compile properly with CLANG).

Does anyone has an idea?

Can I "rescue" the old installed lang/gcc as a package somehow to
attempt a reinstallation in case deletion and recompiling the port will
fail?

Regards,

Oliver


[...]
cc -O2 -pipe -O3 -march=native -I/usr/local/include -fno-strict-aliasing
 -o fixincl fixincl.o fixtests.o fixfixes.o server.o procopen.o fixlib.o
fixopts.o ../libiberty/libiberty.a
echo timestamp > full-stamp
srcdir="../.././../gcc-4.6.3/fixincludes" /bin/sh
../.././../gcc-4.6.3/fixincludes/mkfixinc.sh x86_64-portbld-freebsd10.0
sed -e 's/_at_gcc_version_at_/4.6.3/' < mkheaders.almost > mkheadersT
mv -f mkheadersT mkheaders
gmake[3]: Leaving directory
`/usr/ports/lang/gcc/work/build/build-x86_64-portbld-freebsd10.0/fixincludes'
Configuring stage 1 in ./libcpp
configure: creating cache ./config.cache
checking build system type... x86_64-portbld-freebsd10.0
checking host system type... x86_64-portbld-freebsd10.0
checking target system type... x86_64-portbld-freebsd10.0
checking whether gmake sets $(MAKE)... yes
checking for a BSD-compatible install... /usr/bin/install -c -o root -g
wheel
checking for x86_64-portbld-freebsd10.0-gcc... cc
checking for C compiler default output file name... a.out
checking whether the C compiler works... yes
checking whether we are cross compiling... no
checking for suffix of executables...
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether cc accepts -g... yes
checking for cc option to accept ISO C89... none needed
checking whether we are using the GNU C++ compiler... yes
checking whether c++ accepts -g... yes
checking for x86_64-portbld-freebsd10.0-ranlib... /usr/local/bin/ranlib
checking how to run the C preprocessor... cpp
checking for grep that handles long lines and -e... /usr/bin/grep
checking for egrep... /usr/bin/grep -E
checking for ANSI C header files... yes
checking for sys/types.h... yes
checking for sys/stat.h... yes
checking for stdlib.h... yes
checking for string.h... yes
checking for memory.h... yes
checking for strings.h... yes
checking for inttypes.h... yes
checking for stdint.h... yes
checking for unistd.h... yes
checking minix/config.h usability... no
checking minix/config.h presence... no
checking for minix/config.h... no
checking whether it is safe to define __EXTENSIONS__... yes
checking for special C compiler options needed for large files... no
checking for _FILE_OFFSET_BITS value needed for large files... no
checking for aclocal... aclocal
checking for autoconf... autoconf
checking for autoheader... autoheader
checking whether cc supports -W... yes
checking whether cc supports -Wall... yes
checking whether cc supports -Wwrite-strings... yes
checking whether cc supports -Wmissing-format-attribute... yes
checking whether cc supports -Wstrict-prototypes... yes
checking whether cc supports -Wmissing-prototypes... yes
checking whether cc supports -Wold-style-definition... yes
checking whether cc supports -Wc++-compat... yes
checking whether cc supports -pedantic -Wno-long-long... yes
checking dependency style of cc... none
configure: error: no usable dependency style found
gmake[2]: *** [configure-stage1-libcpp] Error 1
gmake[2]: Leaving directory `/usr/ports/lang/gcc/work/build'
gmake[1]: *** [stage1-bubble] Error 2
gmake[1]: Leaving directory `/usr/ports/lang/gcc/work/build'
gmake: *** [all] Error 2
*** [do-build] Error code 1

Stop in /usr/ports/lang/gcc.
*** [build] Error code 1

Stop in /usr/ports/lang/gcc.

===>>> make failed for lang/gcc
===>>> Aborting update