libssh: split headers to "dev" output

[trofi]

Description of changes

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 23.05 Release Notes (or backporting 22.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

[vcunat]

Apparently cmake has issues detecting this:
https://hydra.nixos.org/build/221540008/nixlog/3/tail

[trofi]

Looking.

[trofi]

Yeah, it's a libssh limitation: it points INTERFACE_INCLUDE_DIRECTORIES to .out, not .dev input:

$ cat /nix/store/rziks5s118dcd2k3c5q8lzlvlgjy718k-libssh-0.10.5-dev/lib/cmake/libssh/libssh-config.cmake
...
# The installation prefix configured by this project.
set(_IMPORT_PREFIX "/nix/store/v7dd8q4mxkycfy7kr71zaiby62lbm1yk-libssh-0.10.5")

# Create imported target ssh
add_library(ssh SHARED IMPORTED)

set_target_properties(ssh PROPERTIES
  INTERFACE_INCLUDE_DIRECTORIES "${_IMPORT_PREFIX}/include"
)

Proposed a revert: #234788