fix tmpfiles 0755 permissions conflict on split roots for subdirs

[nazarewk]

fixes #20

This is MVP that works for me, not 100% sure it's "conceptually" correct.

The reasoning behind it can be found in the linked issue.

Turns

nix-repl> :p lib.pipe nixosConfigurations.brys.config.preservation.preserveAt [(lib.mapAttrsToList (k: e: e.users.kdn.directories)) lib.flatten (builtins.filter (e: e.directory == "/home/kdn/.local/share/bottles"))]
[
  {
    configureParent = false;
    directory = "/home/kdn/.local/share/bottles";
    group = "users";
    how = "_intermediate";
    inInitrd = false;
    mode = "0755";
    user = "kdn";
  }
  {
    configureParent = false;
    createLinkTarget = false;
    directory = "/home/kdn/.local/share/bottles";
    group = "users";
    how = "bindmount";
    inInitrd = false;
    mode = "0750";
    mountOptions = [
      {
        name = "bind";
        value = null;
      }
      {
        name = "X-fstrim.notrim";
        value = null;
      }
      {
        name = "x-gvfs-hide";
        value = null;
      }
      {
        name = "x-gdu.hide";
        value = null;
      }
    ];
    parent = {
      group = "users";
      mode = "0750";
      user = "kdn";
    };
    user = "kdn";
  }
]

into:

nix-repl> :p lib.pipe nixosConfigurations.brys.config.preservation.preserveAt [(lib.mapAttrsToList (k: e: e.users.kdn.directories)) lib.flatten (builtins.filter (e: e.directory == "/home/kdn/.local/share/bottles"))]
[
  {
    configureParent = {
      _type = "override";
      content = false;
      priority = 1000;
    };
    directory = "/home/kdn/.local/share/bottles";
    group = {
      _type = "override";
      content = "users";
      priority = 1000;
    };
    how = {
      _type = "override";
      content = "_intermediate";
      priority = 1000;
    };
    inInitrd = false;
    mode = {
      _type = "override";
      content = "0755";
      priority = 1000;
    };
    user = {
      _type = "override";
      content = "kdn";
      priority = 1000;
    };
  }
  {
    configureParent = false;
    createLinkTarget = false;
    directory = "/home/kdn/.local/share/bottles";
    group = "users";
    how = "bindmount";
    inInitrd = false;
    mode = "0750";
    mountOptions = [
      {
        name = "bind";
        value = null;
      }
      {
        name = "X-fstrim.notrim";
        value = null;
      }
      {
        name = "x-gvfs-hide";
        value = null;
      }
      {
        name = "x-gdu.hide";
        value = null;
      }
    ];
    parent = {
      group = "users";
      mode = "0750";
      user = "kdn";
    };
    user = "kdn";
  }
]