How to add library headers to common scope - c

Question

I have following project structure:
Project
|-include
| |-somedir
| | |-someheader.h
|-src
| |-somedir
| | |-somesource.c
| | |-CMakeLists.txt
| |-main.c
| |-CMakeLists.txt
|-lib
| |-somelib
| | |-include
| | | |-somelibheader.h
| | |-src
| | | |-somelibsource.c
| | | |-CMakeLists.txt
| | |-CMakeLists.txt
| |-CMakeLists.txt
|-CMakeLists.txt
Project/CMakeLists.txt:
cmake_minimum_required(VERSION 3.13)
set(CMAKE_C_STANDARD 11)
project(Project)
list(APPEND INCLUDES ${CMAKE_SOURCE_DIR}/include) # Contains all headers will be add to target
set(LIBRARIES_ROOT ${CMAKE_SOURCE_DIR}/lib)
set(SOURCES_ROOT ${CMAKE_SOURCE_DIR}/src)
add_subdirectory(${LIBRARIES_ROOT})
add_subdirectory(${SOURCES_ROOT})
Project/src/CMakeLists.txt:
add_executable(${CMAKE_PROJECT_NAME} main.c)
target_include_directories(${CMAKE_PROJECT_NAME} PRIVATE ${INCLUDES}) # adding headers
target_link_libraries(${CMAKE_PROJECT_NAME} ${LIBRARIES}) # linking libraries
add_subdirectory(somedir)
Project/src/somedir/CMakeLists.txt:
target_sources(${CMAKE_PROJECT_NAME} PRIVATE somesource.c)
Project/lib/CMakeLists.txt:
add_subdirectory(somelib)
Project/lib/somelib/CMakeLists.txt:
add_library(somelib)
target_include_directories(somelib PRIVATE include)
list(APPEND INCLUDES include) # Adding lib headers to be included to target
list(APPEND LIBRARIES somelib) # Adding lib to be linked to target
add_subdirectory(src)
Project/lib/somelib/src/CMakeLists.txt:
target_sources(somelib PRIVATE somelibsource.c)
In main.c project headers are able to be included, like #include <somedir/someheader.h>, but library header doesn't. It requires relative to main.c path, like #include "../lib/somelib/include/somelibheader.h". How to fix it and add library headers to common scope?