Fix: always use an interface lib for flatsample

[jtdavis777]

Fixes #8889

I'm not sure why the STATIC fallback case exists, so removing it.

[fliiiix]

I don't know about the MSVC case but i added the second case for old cmake versions here #8173 i think we break cmake older than 3.20.0 (https://github.com/Kitware/CMake/releases/tag/v3.20.0 released 2021)

I guess this will still break older systems like debian bullseye https://packages.debian.org/bullseye/cmake

If we want to do that i would propose to set cmake_minimum_required to 3.20.0

[jtdavis777]

We definitely can't do that -- what specifically breaks in the older versions? Interface libs have been supported since 3.0

[fliiiix]

It might be supported since 3.0 but it it started working properly only with 3.20 or something.

cmake ..
CMake Warning at CMake/Version.cmake:35 (message):
  git is not found
Call Stack (most recent call first):
  CMakeLists.txt:5 (include)


-- Proceeding with version: 25.12.19.0
-- The CXX compiler identification is GNU 10.2.1
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Looking for strtof_l
-- Looking for strtof_l - found
-- Looking for strtoull_l
-- Looking for strtoull_l - found
-- Looking for realpath
-- Looking for realpath - found
-- CMAKE_CXX_FLAGS: 
CMake Error at CMakeLists.txt:584 (set_target_properties):
  INTERFACE_LIBRARY targets may only have whitelisted properties.  The
  property "LINKER_LANGUAGE" is not allowed.


CMake Generate step failed.  Build files cannot be regenerated correctly.

To reproduce ->

podman run -it --rm --volume $(pwd):/ws --workdir /ws debian:bullseye

# inside the container
apt update && apt install cmake g++
mkdir build-cmake && cd build-cmake
cmake ..

But it looks like it is already broken right now (using the type STATIC)->

CMake Error at CMakeLists.txt:578 (add_library):
  No SOURCES given to target: flatsample

[fliiiix]

looking at the issue again i would propose to remove this line (578) as well and then it works with old cmake version, no idea about the MSVC case but i prose to fix that later if that still breaks for someone and we understand what the issues is

[jtdavis777]

Yeah the static failure is what was reported in the issue I'm looking to fix. Thanks for the repro steps!!