The bug is not reproducible, so it is likely a hardware or OS problem.
make[2]: *** [.obj/release-shared/helpdialog.o] Erreur 1
make[2]: *** Attente des tâches non terminées....
make[2]: quittant le répertoire « /var/tmp/portage/x11-libs/qt-4.3.3/work/qt-x11-opensource-src-4.3.3/tools/assistant »
make[1]: *** [sub-assistant-all-ordered] Erreur 2
make[1]: quittant le répertoire « /var/tmp/portage/x11-libs/qt-4.3.3/work/qt-x11-opensource-src-4.3.3/tools »
make: *** [sub-tools-all-ordered] Erreur 2
 *
 * ERROR: x11-libs/qt-4.3.3 failed.
 * Call stack:
 *         ebuild.sh, line 1701:  Called dyn_compile
 *         ebuild.sh, line 1039:  Called qa_call 'src_compile'
 *         ebuild.sh, line   44:  Called src_compile
 *   qt-4.3.3.ebuild, line  229:  Called die
 * The specific snippet of code:
 *      emake all || die
 *  The die message:
 *   (no error message)
 *
 * 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/x11-libs/qt-4.3.3/temp/build.log'.
 *
 
 * Messages for package x11-libs/qt-4.3.3:
 
 *
 * ERROR: x11-libs/qt-4.3.3 failed.
 * Call stack:
 *         ebuild.sh, line 1701:  Called dyn_compile
 *         ebuild.sh, line 1039:  Called qa_call 'src_compile'
 *         ebuild.sh, line   44:  Called src_compile
 *   qt-4.3.3.ebuild, line  229:  Called die
 * The specific snippet of code:
 *      emake all || die
 *  The die message:
 *   (no error message)
 *
 * 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/x11-libs/qt-4.3.3/temp/build.log'.
 *