After portsnap fetch update (or portsnap fetch extract), due to some options in make.conf, I get the error:

Building new INDEX files... done.
Generating INDEX-11 - please wait..--- describe.accessibility ---
--- describe.arabic ---
--- describe.archivers ---
--- describe.astro ---
--- describe.audio ---
--- describe.benchmarks ---
--- describe.biology ---
--- describe.cad ---
--- describe.chinese ---
--- describe.comms ---
--- describe.converters ---
--- describe.databases ---
--- describe.deskutils ---
--- describe.devel ---
--- describe.dns ---
--- describe.editors ---
--- describe.emulators ---
--- describe.finance ---
--- describe.french ---
--- describe.ftp ---
--- describe.games ---
--- describe.german ---
--- describe.graphics ---
--- describe.hebrew ---
--- describe.hungarian ---
--- describe.irc ---
--- describe.japanese ---
--- describe.java ---
--- describe.korean ---
--- describe.lang ---
--- describe.mail ---
--- describe.math ---
--- describe.misc ---
--- describe.multimedia ---
--- describe.net ---
--- describe.net-im ---
--- describe.net-mgmt ---
--- describe.net-p2p ---
--- describe.news ---
--- describe.palm ---
--- describe.polish ---
--- describe.ports-mgmt ---
--- describe.portuguese ---
--- describe.print ---
--- describe.russian ---
--- describe.science ---
--- describe.security ---
--- describe.shells ---
--- describe.sysutils ---
--- describe.textproc ---
--- describe.ukrainian ---
--- describe.vietnamese ---
--- describe.www ---
--- describe.x11 ---
--- describe.x11-clocks ---
--- describe.x11-drivers ---
--- describe.x11-fm ---
--- describe.x11-fonts ---
--- describe.x11-servers ---
--- describe.x11-themes ---
--- describe.x11-toolkits ---
--- describe.x11-wm ---
make_index: /usr/ports/x11/nvidia-driver: no entry for /usr/ports/graphics/linux-c6-libglvnd
 Done.

It is the problem I've mentioned on the forum
https://forums.freebsd.org/threads/make-index-do-not-make-index.71487/