/usr/bin/splitindex is in texlive-latex-extra 2016.20170123-5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/bin/../share/texlive/texmf-dist/scripts/splitindex/splitindex.pl
/usr/bin/../share/texlive/texmf-dist/scripts/splitindex/splitindex.pl