How can I get the source directory from an imported target? - cmake

Question

I'm working on a C++ game library. The game library is exporting a package from it's source tree like this:
set(GAMELIB_CONFIG_PATH "lib/cmake/gamelib")
# installation target
install(
FILES
"${CMAKE_CURRENT_BINARY_DIR}/${GAMELIB_CONFIG_PATH}/gamelibConfig.cmake"
DESTINATION ${GAMELIB_CONFIG_PATH}
)
install(
EXPORT gamelibTargets FILE gamelibTargets.cmake
NAMESPACE gamelib::
DESTINATION ${GAMELIB_CONFIG_PATH}
)
# export package from build directory
export(
EXPORT gamelibTargets
FILE "${CMAKE_CURRENT_BINARY_DIR}/gamelibTargets.cmake"
NAMESPACE gamelib::
)
export(PACKAGE gamelib)
So then I got two choices to consume the game library: I can either install the game library and let other project use it from the installation, or I can import it directly from the built source tree, which makes it convenient to develop the engine while also developing a game.
Game are simply importing the package like that:
find_package(gamelib REQUIRED)
target_link_libraries(game PUBLIC gamelib::gamelib)
Here's my problem: How can I get the source path for an imported cmake package? And how can I get a different path when the package is actually installed? I want to ship predefined assets directly from the game lib instead of copying them manually into games. The game will need to read the files from the game library to load them. So I need thier paths either in the source tree, or in the installed path.
When importing, I have gamelib_DIR defined, but that point to the binary dir.
I am familiar with generator expression to set a different value in different contexts:
target_include_directories(gamelib-common INTERFACE
$<INSTALL_INTERFACE:${GAMELIB_INSTALL_INCLUDE_DIR}>
$<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
)
Can something similar be done with source directory and installed path?