Hello all, I have updated my use flags.

USE="X aac aiglx alsa aoss asf bzip2 cairo dbus dvd emerald fam firefox gif
     glitz gnome gstreamer gtk hal java jpeg mad mp3 mp4 new-login nptl
     nptlonly nsplugin opengl pdf png samba spell sqlite svg symlink threads
     tiff truetype unicode x264 xcomposite xinerama xml xorg xscreensaver xv
     xvid -arts -eds -esd -fortran -ipv6 -kde -qt3 -qt4"

And then tried :
emerge -vuD --newuse world

It failed with the error:
=============================================================
checking whether the C compiler works... configure: error: cannot run C
compiled programs.
If you meant to cross compile, use `--host'.
See `config.log' for more details.
make[2]: *** [configure-target-libstdc++-v3] Error 1
make[2]: Leaving directory `/var/tmp/portage/sys-devel/gcc-4.1.2/work/build'
make[1]: *** [all] Error 2
make[1]: Leaving directory `/var/tmp/portage/sys-devel/gcc-4.1.2/work/build'
make: *** [profiledbootstrap] Error 2
 *
 * ERROR: sys-devel/gcc-4.1.2 failed.
 * Call stack:
 *               ebuild.sh, line   49:  Called src_compile
 *             environment, line 4646:  Called toolchain_src_compile
 *             environment, line 5164:  Called gcc_src_compile
 *             environment, line 2972:  Called gcc_do_make
 *             environment, line 2795:  Called die
 * The specific snippet of code:
 *       emake LDFLAGS="${LDFLAGS}" STAGE1_CFLAGS="${STAGE1_CFLAGS}"
LIBPATH="${LIBPATH}" BOOT_CFLAGS="${BOOT_CFLAGS}" ${GCC_MAKE_TARGET} || die
"emake failed with ${GCC_MAKE_TARGET}";
 *  The die message:
 *   emake failed with profiledbootstrap
 *
 * If you need support, post the topmost build error, and the call stack if
relevant.
 * A complete build log is located at
'/var/tmp/portage/sys-devel/gcc-4.1.2/temp/build.log'.
 * The ebuild environment file is located at
'/var/tmp/portage/sys-devel/gcc-4.1.2/temp/environment'.
 *

 * Messages for package app-editors/nano-2.1.5:

 * More helpful info about nano, visit the GDP page:
 * http://www.gentoo.org/doc/en/nano-basics-guide.xml

 * Messages for package sys-devel/gcc-4.1.2:

 *
 * ERROR: sys-devel/gcc-4.1.2 failed.
 * Call stack:
 *               ebuild.sh, line   49:  Called src_compile
 *             environment, line 4646:  Called toolchain_src_compile
 *             environment, line 5164:  Called gcc_src_compile
 *             environment, line 2972:  Called gcc_do_make
 *             environment, line 2795:  Called die
 * The specific snippet of code:
 *       emake LDFLAGS="${LDFLAGS}" STAGE1_CFLAGS="${STAGE1_CFLAGS}"
LIBPATH="${LIBPATH}" BOOT_CFLAGS="${BOOT_CFLAGS}" ${GCC_MAKE_TARGET} || die
"emake failed with ${GCC_MAKE_TARGET}";
 *  The die message:
 *   emake failed with profiledbootstrap
 *
 * If you need support, post the topmost build error, and the call stack if
relevant.
 * A complete build log is located at
'/var/tmp/portage/sys-devel/gcc-4.1.2/temp/build.log'.
 * The ebuild environment file is located at
'/var/tmp/portage/sys-devel/gcc-4.1.2/temp/environment'.
 *
 * Regenerating GNU info directory index...
 * Processed 132 info files.
 * IMPORTANT: 3 config files in '/etc' need updating.
 * See the CONFIGURATION FILES section of the emerge
 * man page to learn how to update config files.
=============================================================
The log file:

checking for x86_64-pc-linux-gnu-gcc...
/var/tmp/portage/sys-devel/gcc-4.1.2/work/build/./gcc/xgcc
-B/var/tmp/portage/sys-devel/gcc-4.1.2/work/build/./gcc/
-B/usr/x86_64-pc-linux-gnu/bin/ -B/usr/x86_64-pc-linux-gnu/lib/ -isystem
/usr/x86_64-pc-linux-gnu/include -isystem
/usr/x86_64-pc-linux-gnu/sys-include  -m32
checking for C compiler default output file name... a.out
checking whether the C compiler works... configure: error: cannot run C
compiled programs.
If you meant to cross compile, use `--host'.
See `config.log' for more details.
make[2]: *** [configure-target-libstdc++-v3] Error 1
make[2]: Leaving directory `/var/tmp/portage/sys-devel/gcc-4.1.2/work/build'
make[1]: *** [all] Error 2
make[1]: Leaving directory `/var/tmp/portage/sys-devel/gcc-4.1.2/work/build'
make: *** [profiledbootstrap] Error 2
 *
 * ERROR: sys-devel/gcc-4.1.2 failed.
 * Call stack:
 *               ebuild.sh, line   49:  Called src_compile
 *             environment, line 4646:  Called toolchain_src_compile
 *             environment, line 5164:  Called gcc_src_compile
 *             environment, line 2972:  Called gcc_do_make
 *             environment, line 2795:  Called die
 * The specific snippet of code:
 *       emake LDFLAGS="${LDFLAGS}" STAGE1_CFLAGS="${STAGE1_CFLAGS}"
LIBPATH="${LIBPATH}" BOOT_CFLAGS="${BOOT_CFLAGS}" ${GCC_MAKE_TARGET} || die
"emake failed with ${GCC_MAKE_TARGET}";
 *  The die message:
 *   emake failed with profiledbootstrap
 *
 * If you need support, post the topmost build error, and the call stack if
relevant.
 * A complete build log is located at
'/var/tmp/portage/sys-devel/gcc-4.1.2/temp/build.log'.
 * The ebuild environment file is located at
'/var/tmp/portage/sys-devel/gcc-4.1.2/temp/environment'.
 *


Any idea ?