Compile steps

gistfile1.txt

> rm -rf flextesa
> git clone git@gitlab.com:tezos/flextesa.git
> cd flextesa
> opam switch create . ocaml-base-compiler.4.09.1
> opam switch import --switch some-name src/tezos-master.opam-switch
> eval $(opam env)
> eval $(opam env)
> make vendors
> make

then following the prompts:

 > dune external-lib-deps --missing src/test/main.exe src/app/main.exe

 > opam install base bigstring cmdliner cohttp-lwt-unix data-encoding dum easy-format ezjsonm fmt genspio hacl-star hex ipaddr lwt lwt-canceler lwt_log mtime ppx_sexp_conv ptime resto resto-cohttp resto-cohttp-client resto-directory ringo secp256k1-internal uutf zarith

    The following actions will be performed
        . . . . .
        (- install re   1.9.0   [required by cohttp])
        . . . . .

then again
> make

      dune build src/test/main.exe src/app/main.exe && \
                  ln -sf _build/default/src/app/main.exe flextesa
      File "local-vendor/tezos-master/src/lib_clic/clic.ml", line 236, characters 12-29:
      236 |       match Re.Str.full_split regex str with
                      ^^^^^^^^^^^^^^^^^
      Error: Unbound module Re
      File "local-vendor/tezos-master/src/lib_stdlib_unix/file_event_sink.ml",
            line 74, characters 22-27:
      74 |     | Name_matches of Re.re
                                ^^^^^
      Error: Unbound module Re