$ emerge --info =www-client/firefox-15.0.1
Portage 2.2.0_alpha141 (default/linux/amd64/10.0/desktop/kde, gcc-4.6.3, glibc-2.15-r3, 3.6.0-gentoo x86_64)
=================================================================
 System Settings
=================================================================
System uname: Linux-3.6.0-gentoo-x86_64-AMD_Phenom-tm-_II_X4_945_Processor-with-gentoo-2.2
Timestamp of tree: Sat, 20 Oct 2012 06:15:01 +0000
distcc 3.1 x86_64-pc-linux-gnu [disabled]
ccache version 3.1.8 [disabled]
app-shells/bash: 4.2_p37
dev-java/java-config: 2.1.12
dev-lang/python: 2.4.6, 2.5.4-r4, 2.6.8, 2.7.3-r2, 3.2.3-r1
dev-util/ccache: 3.1.8
dev-util/cmake: 2.8.9-r1
dev-util/pkgconfig: 0.27.1
sys-apps/baselayout: 2.2
sys-apps/openrc: 0.11.1
sys-apps/sandbox: 2.6
sys-devel/autoconf: 2.13, 2.69
sys-devel/automake: 1.9.6-r3, 1.10.3, 1.11.6, 1.12.4
sys-devel/binutils: 2.22.90
sys-devel/gcc: 3.4.6-r2, 4.1.2, 4.5.4, 4.6.3, 4.7.1
sys-devel/gcc-config: 1.7.3
sys-devel/libtool: 2.4.2
sys-devel/make: 3.82-r4
sys-kernel/linux-headers: 3.6 (virtual/os-headers)
sys-libs/glibc: 2.15-r3
Repositories: gentoo java-overlay sage-on-gentoo sunrise-enabled bump generated bugfix mvg-java-experimental mvgLocal
ACCEPT_KEYWORDS="amd64 ~amd64"
ACCEPT_LICENSE="* -@EULA dlj-1.1 sun-bcla-java-vm Oracle-BCLA-JavaSE skype-eula skype-4.0.0.7-copyright googleearth AdobeFlash-10.3 PUEL"
CBUILD="x86_64-pc-linux-gnu"
CFLAGS="-march=amdfam10 -O2 -ggdb -pipe"
CHOST="x86_64-pc-linux-gnu"
CONFIG_PROTECT="/etc /usr/share/config /usr/share/gnupg/qualified.txt /usr/share/maven-bin-3.0/conf /usr/share/openvpn/easy-rsa /usr/share/themes/oxygen-gtk/gtk-2.0 /var/lib/hsqldb"
CONFIG_PROTECT_MASK="/etc/ca-certificates.conf /etc/dconf /etc/env.d /etc/fonts/fonts.conf /etc/gconf /etc/gentoo-release /etc/php/apache2-php5.3/ext-active/ /etc/php/apache2-php5.4/ext-active/ /etc/php/cgi-php5.3/ext-active/ /etc/php/cgi-php5.4/ext-active/ /etc/php/cli-php5.3/ext-active/ /etc/php/cli-php5.4/ext-active/ /etc/revdep-rebuild /etc/sandbox.d /etc/terminfo /etc/texmf/language.dat.d /etc/texmf/language.def.d /etc/texmf/updmap.d /etc/texmf/web2c"
CXXFLAGS="-march=amdfam10 -O2 -ggdb -pipe"
DISTDIR="/usr/portage/distfiles"
FCFLAGS="-O2 -pipe"
FEATURES="assume-digests binpkg-logs collision-protect config-protect-if-modified distlocks ebuild-locks fixlafiles news parallel-fetch preserve-libs protect-owned sandbox sfperms splitdebug strict unknown-features-warn unmerge-logs unmerge-orphans userfetch xattr"
FFLAGS="-O2 -pipe"
GENTOO_MIRRORS="http://mirror.cambrium.nl/pub/os/linux/gentoo/ http://mirror.leaseweb.com/gentoo/ ftp://mirror.netcologne.de/gentoo/"
LANG="de_DE.utf8"
LDFLAGS="-Wl,--as-needed"
LINGUAS="en de en_US en_GB"
MAKEOPTS="-j5"
PKGDIR="/usr/portage/packages"
PORTAGE_CONFIGROOT="/"
PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --compress --force --whole-file --delete --stats --human-readable --timeout=180 --exclude=/distfiles --exclude=/local --exclude=/packages"
PORTAGE_TMPDIR="/var/tmp"
PORTDIR="/usr/portage"
PORTDIR_OVERLAY="/usr/portage/local/layman/java-overlay /usr/portage/local/layman/sage-on-gentoo /usr/portage/local/sunrise-enabled /usr/portage/local/bump /usr/portage/local/generated /usr/portage/local/bugfix /usr/portage/local/mvg-java /usr/portage/local/mvg"
SYNC="rsync://rsync.de.gentoo.org/gentoo-portage"
USE="X a52 aac acl acpi alsa amd64 apache2 audiofile avahi bash-completion bcmath berkdb branding bzip2 c++ cairo cdda cdparanoia cdr chroot cli consolekit cracklib crypt css cups curl cxx dba dbus declarative dhcp doc dri dts dv dvd dvdr emacs emboss encode escreen exif fam fastcgi ffmpeg fftw firefox flac flatfile fortran ftp gcc-libffi gd gdbm gif gimp gnutls gphoto2 gpm graphviz gs gstreamer gtk gtk3 hal hbci html iconv icu idn imagemagick ipv6 iso14755 ithreads jabber jack java jpeg jpeg2k kde kerberos kipi kpathsea kvm ladspa latex lcms ldap leim libnotify lirc lm_sensors logrotate lzma lzo mad maildir mhash midi mikmod mime mjpeg mmx mng modules mozxmlterm mp3 mp4 mpeg mpeg2 mplayer mudflap multilib mysql ncurses network nls nptl nsplugin numpy objc odbc ofx ogg openexr opengl openmp pam pango pcre pdf perl phonon php plasma plotutils png policykit povray ppds pppd procmail python qt3support qt4 quicktime rdesktop readline recode sasl scanner sdl session smime sndfile snmp sockets socks5 sox speex spell sqlite sse sse2 ssl startup-notification subversion svg tcl tcpd theora threads thunderbird tiff timidity tokenizer transcode translator truetype type1 udev udisks unicode upower usb userlocales v4l v4l2 vhosts vorbis vpx wmf wxwidgets x264 xanim xattr xcb xcomposite xine xinerama xinetd xml xprint xscreensaver xulrunner xv xvid xvmc zlib" ALSA_CARDS="bt87x emu10k1x hda-intel usb-audio via82xx via82xx-modem" ALSA_PCM_PLUGINS="adpcm alaw asym copy dmix dshare dsnoop empty extplug file hooks iec958 ioplug ladspa lfloat linear meter mmap_emul mulaw multi null plug rate route share shm softvol" APACHE2_MODULES="actions alias asis auth_basic auth_digest authn_alias authn_anon authn_dbm authn_default authn_file authz_dbm authz_default authz_groupfile authz_host authz_owner authz_user autoindex cache cgi cgid dav dav_fs dav_lock deflate dir disk_cache env expires ext_filter filter headers include info log_config logio mem_cache mime mime_magic negotiation proxy proxy_connect proxy_ftp proxy_http rewrite setenvif speling status unique_id userdir usertrack vhost_alias" APACHE2_MPMS="prefork" CALLIGRA_FEATURES="kexi words flow plan sheets stage tables krita karbon braindump" CAMERAS="ptp2" COLLECTD_PLUGINS="df interface irq load memory rrdtool swap syslog" DRACUT_MODULES="lvm" ELIBC="glibc" FRITZCAPI_CARDS="fcpci" GPSD_PROTOCOLS="ashtech aivdm earthmate evermore fv18 garmin garmintxt gpsclock itrax mtk3301 nmea ntrip navcom oceanserver oldstyle oncore rtcm104v2 rtcm104v3 sirf superstar2 timing tsip tripmate tnt ubx" INPUT_DEVICES="evdev joystick keyboard mouse wacom" KERNEL="linux" LCD_DEVICES="bayrad cfontz cfontz633 glk hd44780 lb216 lcdm001 mtxorb ncurses text" LIBREOFFICE_EXTENSIONS="presenter-console presenter-minimizer" LINGUAS="en de en_US en_GB" LIRC_DEVICES="devinput" MISDN_CARDS="avmfritz" PHP_TARGETS="php5-3" PYTHON_TARGETS="python3_2 python2_7" RUBY_TARGETS="ruby19 jruby" USERLAND="GNU" VIDEO_CARDS="nouveau nv radeon fbdev v4l vesa vga" XTABLES_ADDONS="quota2 psd pknock lscan length2 ipv4options ipset ipp2p iface geoip fuzzy condition tee tarpit sysrq steal rawnat logmark ipmark dhcpmac delude chaos account"
Unset: CPPFLAGS, CTARGET, EMERGE_DEFAULT_OPTS, INSTALL_MASK, LC_ALL, PORTAGE_BUNZIP2_COMMAND, PORTAGE_COMPRESS, PORTAGE_COMPRESS_FLAGS, PORTAGE_RSYNC_EXTRA_OPTS, USE_PYTHON

=================================================================
 Package Settings
=================================================================

www-client/firefox-15.0.1 was built with the following:
USE="alsa (consolekit) dbus gstreamer ipc jit libnotify minimal (multilib) (policykit) startup-notification webm -bindist -custom-cflags -custom-optimization -debug -pgo (-selinux) -system-sqlite -wifi" LINGUAS="de en_GB -af -ak -ar -as -ast -be -bg -bn_BD -bn_IN -br -bs -ca -cs -csb -cy -da -el -en_ZA -eo -es_AR -es_CL -es_ES -es_MX -et -eu -fa -fi -fr -fy_NL -ga_IE -gd -gl -gu_IN -he -hi_IN -hr -hu -hy_AM -id -is -it -ja -kk -km -kn -ko -ku -lg -lt -lv -mai -mk -ml -mr -nb_NO -nl -nn_NO -nso -or -pa_IN -pl -pt_BR -pt_PT -rm -ro -ru -si -sk -sl -son -sq -sr -sv_SE -ta -ta_LK -te -th -tr -uk -vi -zh_CN -zh_TW -zu"
CFLAGS="-march=amdfam10 -ggdb -pipe -mno-avx"
CXXFLAGS="-march=amdfam10 -ggdb -pipe -mno-avx"


$ emerge -pqv =www-client/firefox-15.0.1
[ebuild   R   ] www-client/firefox-15.0.1  USE="alsa dbus gstreamer ipc jit libnotify minimal startup-notification webm -bindist -custom-cflags -custom-optimization -debug -pgo (-selinux) -system-sqlite -wifi" LINGUAS="de en_GB -af -ak -ar -as -ast -be -bg -bn_BD -bn_IN -br -bs -ca -cs -csb -cy -da -el -en_ZA -eo -es_AR -es_CL -es_ES -es_MX -et -eu -fa -fi -fr -fy_NL -ga_IE -gd -gl -gu_IN -he -hi_IN -hr -hu -hy_AM -id -is -it -ja -kk -km -kn -ko -ku -lg -lt -lv -mai -mk -ml -mr -nb_NO -nl -nn_NO -nso -or -pa_IN -pl -pt_BR -pt_PT -rm -ro -ru -si -sk -sl -son -sq -sr -sv_SE -ta -ta_LK -te -th -tr -uk -vi -zh_CN -zh_TW -zu"