GitLab

* Point to updated submodules

* Set TREESITTER_LIBDIR as obtained from pkg-config.

* Call 'make' instead of 'dune build' for the opam install of
semgrep-core.

* Build semgrep-core with simpler 'make' command.

* Update ocaml-tree-sitter submodule to make it set TREESITTER_LIBDIR.

* Use new base image with pre-built dependencies

* Remove reference to 'opam' user account.

* Fix the new home created by GHA

* Use new base image for all semgrep-core builds

* We need to chmod /__w after all.

* Create version.ml from its own script. This script should now fail
properly if the version can't be obtained. Additionally, this attempts a
fix for the git command that fails to produce a version string in some
environments.

* Try to fix the osx build, which uses 'make setup'

Co-authored-by: Martin Jambon <Martin Jambon>