Can't locate Text/Unidecode.pm in @INC (you may need to install the Text::Unidecode module) (@INC contains: /usr/share/texinfo /etc/perl /usr/local/lib64/perl5/5.18.2/x86_64-linux /usr/local/lib64/perl5/5.18.2 /usr/lib64/perl5/vendor_perl/5.18.2/x86_64-linux /usr/lib64/perl5/vendor_perl/5.18.2 /usr/local/lib64/perl5 /usr/lib64/perl5/vendor_perl /usr/lib64/perl5/5.18.2/x86_64-linux /usr/lib64/perl5/5.18.2 .) at /usr/share/texinfo/Texinfo/Convert/NodeNameNormalization.pm line 29.
BEGIN failed--compilation aborted at /usr/share/texinfo/Texinfo/Convert/NodeNameNormalization.pm line 29.
Compilation failed in require at /usr/share/texinfo/Texinfo/Parser.pm line 57.
BEGIN failed--compilation aborted at /usr/share/texinfo/Texinfo/Parser.pm line 57.
Compilation failed in require at /usr/bin/makeinfo line 101.
BEGIN failed--compilation aborted at /usr/bin/makeinfo line 101.
Makefile:394: recipe for target '/var/tmp/portage/dev-util/kbuild-0.1.9998_pre20131130/work/kBuild-0.1.9998-pre20131130/src/sed/doc/sed.info' failed
make[3]: *** [/var/tmp/portage/dev-util/kbuild-0.1.9998_pre20131130/work/kBuild-0.1.9998-pre20131130/src/sed/doc/sed.info] Error 2
make[3]: Leaving directory '/var/tmp/portage/dev-util/kbuild-0.1.9998_pre20131130/work/kBuild-0.1.9998-pre20131130/out/linux.amd64/release/bootstrap/sed/doc'
Makefile:435: recipe for target 'all-recursive' failed
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory '/var/tmp/portage/dev-util/kbuild-0.1.9998_pre20131130/work/kBuild-0.1.9998-pre20131130/out/linux.amd64/release/bootstrap/sed'
Makefile:371: recipe for target 'all' failed
make[1]: *** [all] Error 2
make[1]: Leaving directory '/var/tmp/portage/dev-util/kbuild-0.1.9998_pre20131130/work/kBuild-0.1.9998-pre20131130/out/linux.amd64/release/bootstrap/sed'
bootstrap.gmk:194: recipe for target '/var/tmp/portage/dev-util/kbuild-0.1.9998_pre20131130/work/kBuild-0.1.9998-pre20131130/out/linux.amd64/release/bootstrap/sed/sed/sed' failed
make: *** [/var/tmp/portage/dev-util/kbuild-0.1.9998_pre20131130/work/kBuild-0.1.9998-pre20131130/out/linux.amd64/release/bootstrap/sed/sed/sed] Error 2
kBuild/env.sh: info: rc=2: make -f bootstrap.gmk AUTORECONF=true AR=x86_64-pc-linux-gnu-ar

• ERROR: dev-util/kbuild-0.1.9998_pre20131130 failed (compile phase):
• bootstrap failed
• Call stack:
• ebuild.sh, line 93: Called src_compile
• environment, line 2722: Called die
• The specific snippet of code:
• kBuild/env.sh --full make -f bootstrap.gmk AUTORECONF=true AR="$(tc-getAR)" || die "bootstrap failed"
• If you need support, post the output of `emerge --info '=dev-util/kbuild-0.1.9998_pre20131130'`,
• the complete build log and the output of `emerge -pqv '=dev-util/kbuild-0.1.9998_pre20131130'`.
• The complete build log is located at '/var/tmp/portage/dev-util/kbuild-0.1.9998_pre20131130/temp/build.log'.
• The ebuild environment file is located at '/var/tmp/portage/dev-util/kbuild-0.1.9998_pre20131130/temp/environment'.
• Working directory: '/var/tmp/portage/dev-util/kbuild-0.1.9998_pre20131130/work/kBuild-0.1.9998-pre20131130'
• S: '/var/tmp/portage/dev-util/kbuild-0.1.9998_pre20131130/work/kBuild-0.1.9998-pre20131130'

And it prevents from installing VirtualBox