virtualbox-modules-5.1.8.ebuild contains the code snippet CONFIG_CHECK="!TRIM_UNUSED_KSYMS" ERROR_TRIM_UNUSED_KSYMS="This option removed kernel symbols that are needed by ${PN} to load correctly." But the resulting error does not tell the missing kernel symbol, so users need to read the ebuild to find out. Portage output is * Checking for suitable kernel configuration options... * This option removed kernel symbols that are needed by virtualbox-modules to load correctly. * Please check to make sure these options are set correctly. Please fix the error message.
commit 265a62ee252c5f9efc21061ae358f84e9ef2b00c Author: Lars Wendler <polynomial-c@gentoo.org> Date: Sat Oct 29 21:55:21 2016 app-emulation/virtualbox-modules: Fixed kconfig error message (bug #598266). Package-Manager: portage-2.3.2 Signed-off-by: Lars Wendler <polynomial-c@gentoo.org>