CMake integration available only after install

[v-val]

When trying to use clsocket without installing it (e.g. with FetchContent), include path is not set and compilation fails. With following dummy example: main.cpp:

#include <PassiveSocket.h>
int main() {}

CMakeLists.txt:

project(test_clsocket_cmake LANGUAGES CXX)
set(CMAKE_CXX_STANDARD 17)

include(FetchContent)
FetchContent_Declare(
    clsocket
    GIT_REPOSITORY https://github.com/DFHack/clsocket.git
)
option(CLSOCKET_SHARED Off)
option(CLSOCKET_DEP_ONLY Off)
FetchContent_MakeAvailable(clsocket)

set(app_ ${PROJECT_NAME})
add_executable(${app_} main.cpp)
target_link_libraries(${app_} clsocket)

Pre-build cmake stage passes fine, but the build fails:

[main] Building folder: clsocket-cmake
[build] Starting build
[proc] Executing command: /Users/me/brew/bin/cmake --build /Users/me/src/clsocket-cmake/build --config Debug --target all --
[build] [1/2  50% :: 0.057] Building CXX object CMakeFiles/test_clsocket_cmake.dir/main.o
[build] FAILED: CMakeFiles/test_clsocket_cmake.dir/main.o
[build] /usr/bin/clang++   -g -arch x86_64 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk -std=gnu++17 -MD -MT CMakeFiles/test_clsocket_cmake.dir/main.o -MF CMakeFiles/test_clsocket_cmake.dir/main.o.d -o CMakeFiles/test_clsocket_cmake.dir/main.o -c /Users/me/src/clsocket-cmake/main.cpp
[build] /Users/me/src/clsocket-cmake/main.cpp:1:10: fatal error: 'PassiveSocket.h' file not found
[build] #include <PassiveSocket.h>
[build]          ^~~~~~~~~~~~~~~~~
[build] 1 error generated.
[build] ninja: build stopped: subcommand failed.
[proc] The command: /Users/me/brew/bin/cmake --build /Users/me/src/clsocket-cmake/build --config Debug --target all -- exited with code: 1 and signal: null
[build] Build finished with exit code 1