I Never build artoolkitx under Windows, because I have a Linux machine, for sure it is an error, maybe try to replace that line "D:/a/1/s/Source/depends/windows/lib/x64/pthreadVC2static.lib" with simply pthread. I have no other suggestions...

If I am not mistaking pthread is Linux only. For the msvc on windows you need pthreadVC2. What seems to work is to download it from the sources https://github.com/artoolkitx/artoolkitx/raw/master/Source/depends/windows/lib/x64/pthreadVC2static.lib and exchange D:/a/1/s/Source/depends/windows/lib/x64/pthreadVC2static.lib with a path to the downloaded file. But I guess that is not the intended way to get the sdk for windows.

Yes, you are right for sure this is not the intended way... Sorry, i can not help much on this issue! For sure @philip-lamb or @ThorstenBux may help you.

Im not sure if it is helpful for the issue but CMake does have generator-expressions. $<INSTALL_INTERFACE:...> and $<BUILD_INTERFACE:...> could be useful.

Instead of

target_link_libraries(ARX
   PUBLIC ${PTHREAD_LIBRARIES}
...
)

it could be

install(FILES ${PTHREAD_LIBRARIES} DESTINATION ${ARX_INSTALL_LIBRARY_DIR})
target_link_libraries(ARX
   PUBLIC
      $<BUILD_INTERFACE:${PTHREAD_LIBRARIES}>
      $<INSTALL_INTERFACE:%relativePath%>
...
)

The relative path would need to be composed platform dependent, e.g. for windows it would could be ${ARX_INSTALL_LIBRARY_DIR}/pthreadVC2static.lib. Here is a more detailed description of the feature.

pthreads is used on Windows too via the pthreads-win32 library, which is the one that's being linked here. It's provided in the project (see https://github.com/artoolkitx/artoolkitx/blob/master/Source/depends/windows/lib/x64/pthreadVC2static.lib) but having the full path to that library in the CMake module is obviously a bug.

What I'd suggest as a short-term workaround is to just copy the above library out of artoolkitx into your own link libs folder, and adjust the cmake module path. I'll have to investigate why the full path is being included.