Calculating dependencies... done!
>>> Verifying ebuild Manifests...
>>> starting parallel fetching

>>> Emerging (1 of 3) app-emulation/virtualbox-modules-1.3.8-r2 to /
 * vbox-kernel-module-src-1.3.8.tar.bz2 MD5 ;-) ...                       [ ok ]
 * vbox-kernel-module-src-1.3.8.tar.bz2 RMD160 ;-) ...                    [ ok ]
 * vbox-kernel-module-src-1.3.8.tar.bz2 SHA1 ;-) ...                      [ ok ]
 * vbox-kernel-module-src-1.3.8.tar.bz2 SHA256 ;-) ...                    [ ok ]
 * vbox-kernel-module-src-1.3.8.tar.bz2 size ;-) ...                      [ ok ]
 * checking ebuild checksums ;-) ...                                      [ ok ]
 * checking auxfile checksums ;-) ...                                     [ ok ]
 * checking miscfile checksums ;-) ...                                    [ ok ]
 * checking vbox-kernel-module-src-1.3.8.tar.bz2 ;-) ...                  [ ok ]
 * Determining the location of the kernel source code
 * Found kernel source directory:
 *     /usr/src/linux
 * Could not find a usable .config in the kernel source directory.
 * Please ensure that /usr/src/linux points to a configured set of Linux sources.
 * If you are using KBUILD_OUTPUT, please set the environment var so that
 * it points to the necessary object directory so that it might find .config.

!!! ERROR: app-emulation/virtualbox-modules-1.3.8-r2 failed.
Call stack:
  ebuild.sh, line 1630:   Called dyn_setup
  ebuild.sh, line 702:   Called qa_call 'pkg_setup'
  ebuild.sh, line 44:   Called pkg_setup
  virtualbox-modules-1.3.8-r2.ebuild, line 28:   Called linux-mod_pkg_setup
  linux-mod.eclass, line 464:   Called linux-info_pkg_setup
  linux-info.eclass, line 554:   Called die

!!! Unable to calculate Linux Kernel version
!!! 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/app-emulation/virtualbox-modules-1.3.8-r2/temp/build.log'.

!!! This ebuild is from an overlay: '/usr/portage/local/layman/sabayon'