$ sudo emerge libreoffice
Calculating dependencies... done!
>>> Verifying ebuild manifests
>>> Running pre-merge checks for x11-drivers/xf86-input-wacom-0.36.0-r2
* Determining the location of the kernel source code
* Found kernel source directory:
* /usr/src/linux
* Could not find a Makefile in the kernel source directory.
* Please ensure that /usr/src/linux points to a complete set of Linux sources
* Unable to calculate Linux Kernel version for build, attempting to use running version
>>> Running pre-merge checks for media-libs/libg