Hello. luajit upstream doesn't support ppc64. See bug 554376 or bug 488318. Please add 'luajit' to use.mask on ppc64 arch similarly to how 'luajittex' is in use.mask.
Fixed in commit 046d880c3cba536602cafc350383a40fc492ffbc Author: Ilya Tumaykin <itumaykin@gmail.com> AuthorDate: Sat May 6 02:04:26 2017 +0300 Commit: Michał Górny <mgorny@gentoo.org> CommitDate: Sun May 7 10:23:02 2017 +0200 profiles/arch/powerpc/ppc64/64ul: mask luajit USE, #608326 Closes: https://github.com/gentoo/gentoo/pull/4549