Instead of searching `/usr` it should search for the `xkb`,
$XDG_DATA_DIRS will be searched. With this approach we allow compliance
on NixOS and non-NixOS systems to find `symbols` in the `xkb` directory.

The patch has been accepted by upstream, but isn't released yet, so this
is mainly a temporary fix until we can bump ZSH to the next stable version.

The `xserver` module links `/share/X11/xkb` to `/run/current-system` to
make this possible.

The fix can be tested inside the following VM:

```
{
  zshtest = {
    programs.zsh.enable = true;
    users.extraUsers.vm = {
      password = "vm";
      isNormalUser = true;
    };
    services.xserver.enable = true;
  };
}
```

Fixes NixOS#46025

I'm not sure what the problem is, precisely, but even so
this was preventing use of things like cast'ing--
not that I'm entirely clear on what that would be the case either :/.

Err on caution and let's go back to what the situation was before
and fix it properly when we better understand the issue.

Semi-automatic update generated by
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based on information from
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also simplify include expression a touch

Uses uname data to find what to set these variables:

- CMAKE_SYSTEM_NAME
- CMAKE_SYSTEM_PROCESSOR
- CMAKE_SYSTEM_VERSION
- CMAKE_HOST_SYSTEM_NAME
- CMAKE_HOST_SYSTEM_PROCESSOR
- CMAKE_HOST_SYSTEM_VERSION

the boost url is broken - remove for now

this makes it easier to show what supports windows vs. unix.

"platforms.all" could include any possible os (even a machine with no
OS at all!). We can’t possible hope to support all of that, so need to
be more specific.

avoid mass rebuild from the last commits

We might need OCaml packages that are not the one Coq is depending on
but they still need to come from the same package set (same OCaml version).