dev-libs/skalibs installs the file /etc/ld.so.conf.d/10skalibs.conf containing the path "/lib64/skalibs". However, this directory doesn't exist; the ebuild installs the dynamic libraries to /lib64/ and the static libraries to /usr/lib64/skalibs. Given that the skalibs revdeps s6 and execline build and work fine even without this additional linker configuration, I'd recommend dropping this file entirely instead of fixing the path.
Fixed in dev-libs/skalibs-2.4.0.2.