[Can't Compile vanilla-sources Kernel]

On a side note : there is a Funtoo system resurrection guide @ https://www.funtoo.org/System_resurrection that details the steps @palica just correctly described, but it needs some "modernization/lovin"  to reflect the /usr/portage move to /var/cache and /var/git plus some other minor technical details.

[Can't Compile vanilla-sources Kernel]

Sorry, I was offering advice based on your initial problem with make oldconfig for vanilla sources.  Which points to broken binutils.  From your original question you were rebuilding @world so it appeared that you were able to emerge/build packages. From that point on the thread has evolved into a hodgepodge of many broken things that may or may not have happened after the first question.  At this point though it seems now your compiler links are broken.

[Can't Compile vanilla-sources Kernel]

I would try rebuilding binutils first since it provides the assembler. But if that fails you can rebuild a sane toolchain. emerge in this order gcc binutils glibc

eselect gcc list and eselect gcc set your compiler and source /etc/profile

[apr-util-1.6.0.tar.bz2 ERROR 404: Not Found]

bug was filed a few days ago and should be fixed now. bug FL-4743

[TTY (console) colour changed after OpenRC start]

I thought 4.14.12 was latest stable marked kernel with all the meltdown, spectre patches and that the latest linux-firmware has updated drivers for it.  Probably want the latest microcode too.  could be some PTI thing?? IDK maybe worth a shot making sure you have latest kernel? just throwing out ideas.

[Anonymous usage reports for funtoo kits usage]

looks cool, all the kits seem to be only showing the python-kit version.