Problem building buildroot SVN under ia64

Hello,

I'm trying to compile buildroot SVN (from today) from amd64 to ia64 (itanium2).
The problem occures when compiling the gcc cross compiler (same error on gcc 3.4/4.1.2/4.2.0)
The problem seems to come from "toolchain_build_ia64/gcc-4.2.0/gcc/config.gcc" where
the variable "supported_defaults" is not set for ia64. The result is the following error during gcc compile:

-------------------------------
Checking build system dependencies:

CC clean:                                       Ok
CXX clean:                                      Ok
CPP clean:                                      Ok
CFLAGS clean:                                   Ok
INCLUDES clean:                                 Ok
CXXFLAGS clean:                                 Ok
which installed:                                Ok
sed works:                                      Ok (/bin/sed)

GNU make version '3.81': Ok
C compiler '/usr/bin/gcc'
C compiler version '4.1.2': Ok
C++ compiler '/usr/bin/g++'

C++ compiler version '4.1.2':                   Ok
bison installed:                                Ok
flex installed:                                 Ok
gettext installed:                              Ok
makeinfo installed:                             Ok
Build system dependencies:                      Ok

make -j1 -C /home/users/admin/visconte/pipol-deploy/tests/buildroot/toolchain_build_ia64/gcc-4.2.0-initial

all-gcc
make[1]: Entering directory `/home/users/admin/visconte/pipol-deploy/tests/buildroot/toolchain_build_ia64/gcc-4.2.0-initial' Configuring in ./gcc
configure: loading cache ./config.cache
checking build system type... x86_64-pc-linux-gnu
[...]
checking whether sigaltstack is declared... yes
checking for struct tms... yes
checking for clock_t... yes
checking for .preinit_array/.init_array/.fini_array support... yes
checking if mkdir takes one argument... no
This target does not support --with-tune.
Valid --with options are:
make[1]: *** [configure-gcc] Error 1
make[1]: Leaving directory `/home/users/admin/visconte/pipol-deploy/tests/buildroot/toolchain_build_ia64/gcc-4.2.0-initial'
make: *** [/home/users/admin/visconte/pipol-deploy/tests/buildroot/toolchain_build_ia64/gcc-4.2.0-initial/.compiled]

Error 2
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Cheers,
Fran?ois VISCONTE