CMakeLists.txt

add_library(hello SHARED src/hello.cc)
target_include_directories(hello PUBLIC
    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
    $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
install(TARGETS hello LIBRARY DESTINATION .)

add_library(complex SHARED src/complex.cc)
target_include_directories(complex PUBLIC
    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
    $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
target_link_libraries(complex PRIVATE hello)
install(TARGETS complex LIBRARY DESTINATION .)
set_target_properties(complex PROPERTIES
    INSTALL_RPATH "$ORIGIN"
)

# install(DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/include/"
# DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
# set(HELLO_CMAKE_PACKAGE_INSTALL_SUBDIR "share/hello/cmake")

# install(
# EXPORT helloTargets
# NAMESPACE hello::
# DESTINATION ${HELLO_CMAKE_PACKAGE_INSTALL_SUBDIR})