The simplest way to install VST is to install the Coq Platform. A Coq Platform release in approximately August 2021 will include VST 2.8.
Until then, the best way to install VST 2.8 is through opam: from the coq-released repository, install package coq-vst, version 2.8.
One method of doing that is:
- Install the Coq Platform 2021.02.1 release using the "Compiling from Sources via opam" method; in that process unselect (do not install) CompCert and VST.
- Then do
opam update; opam install coq-vst
which will install the latest CompCert and VST.