Updating Installation Docs

[ASRagab]

If you follow the current instructions for creating a hello world project, when running dune exec hello you receive the following error:

Error: I cannot find the root of the current workspace/project.
If you would like to create a new dune project, you can type:

    dune init project NAME

Otherwise, please make sure to run dune inside an existing project or
workspace. For more information about how dune identifies the root of the
current workspace/project, please refer to
https://dune.readthedocs.io/en/stable/usage.html#finding-the-root

I believe this has to do with the changed behavior of dune exec/build which will not create a dune-project for you anymore if it is missing.

After creating the file with the minimum required contents as seen on dune.build, the next error received is:

File "dune", line 1, characters 0-47:
1 | (executable
2 |  (name hello)
3 |  (public_name hello))
Error: The current project defines some public elements, but no opam packages
are defined.
Please add a <package>.opam file at the project root so that these elements
are installed into it.

If you dutifully follow the suggestion and add an empty hello.opam the project will build the exe and execute the binary

❯ dune build hello.exe
❯ dune exec hello
Hello, World!

It is of course possible that I missed a step, but this seems to be the minimum viable project, i.e as opposed to doing dune init proj ...

[gabriel-bezerra]

These changes worked for me when trying to follow the installation guide.

[davesnx]

Thanks!