hackenherr ~ #  emerge-world                                                                                                                                                           [22:28:16]
[ebuild  NS   ] sys-kernel/pf-sources-4.0_p2 [4.0_p1] USE="symlink -build" 
[ebuild     U ] x11-themes/light-themes-15.04_p20150410 [0.1.93-r4] USE="gtk3" 

Would you like to merge these packages? [Yes/No] 
>>> Verifying ebuild manifests
>>> Running pre-merge checks for sys-kernel/pf-sources-4.0_p2
 * 
 * pf-sources-4.0_p2 needs an active GCC 4.9+ compiler
 * 
 * ERROR: sys-kernel/pf-sources-4.0_p2 failed (pretend phase):
 *   pf-sources-4.0_p2 needs an active sys-devel/gcc >= 4.9
 * 
 * Call stack:
 *                  ebuild.sh, line  93:  Called pkg_pretend
 *   pf-sources-4.0_p2.ebuild, line  47:  Called die
 * The specific snippet of code:
 *   			die "${P} needs an active sys-devel/gcc >= 4.9"
 * 
 * If you need support, post the output of `emerge --info '=sys-kernel/pf-sources-4.0_p2'`,
 * the complete build log and the output of `emerge -pqv '=sys-kernel/pf-sources-4.0_p2'`.
 * The complete build log is located at '/var/tmp/portage/sys-kernel/pf-sources-4.0_p2/temp/build.log'.
 * The ebuild environment file is located at '/var/tmp/portage/sys-kernel/pf-sources-4.0_p2/temp/die.env'.
 * Working directory: '/usr/lib64/portage/pym'
 * S: '/var/tmp/portage/sys-kernel/pf-sources-4.0_p2/work/linux-4.0_p2-pf'

 * Messages for package sys-kernel/pf-sources-4.0_p2:

 * 
 * pf-sources-4.0_p2 needs an active GCC 4.9+ compiler
 * 
 * ERROR: sys-kernel/pf-sources-4.0_p2 failed (pretend phase):
 *   pf-sources-4.0_p2 needs an active sys-devel/gcc >= 4.9
 * 
 * Call stack:
 *                  ebuild.sh, line  93:  Called pkg_pretend
 *   pf-sources-4.0_p2.ebuild, line  47:  Called die
 * The specific snippet of code:
 *   			die "${P} needs an active sys-devel/gcc >= 4.9"
 * 
 * If you need support, post the output of `emerge --info '=sys-kernel/pf-sources-4.0_p2'`,
 * the complete build log and the output of `emerge -pqv '=sys-kernel/pf-sources-4.0_p2'`.
 * The complete build log is located at '/var/tmp/portage/sys-kernel/pf-sources-4.0_p2/temp/build.log'.
 * The ebuild environment file is located at '/var/tmp/portage/sys-kernel/pf-sources-4.0_p2/temp/die.env'.
 * Working directory: '/usr/lib64/portage/pym'
 * S: '/var/tmp/portage/sys-kernel/pf-sources-4.0_p2/work/linux-4.0_p2-pf'