CMake Library from subdirectory

I'm trying to build a C++ project using CMake. Therefore I'd like to create a library from a subdirectory. My project structure looks like the following:

project
  core
    CMakeLists.txt
    point.h
    point.cpp
  CMakeLists.txt
  build
  main.cpp

My outer CMakeLists.txt:

cmake_minimum_required(VERSION 3.5)

project(MyProject)

include_directories(${CMAKE_CURRENT_SOURCE_DIR})

add_subdirectory(core)

add_executable(main main.cpp)

target_link_libraries(main core)

My inner CMakeLists.txt:

add_library(
    core
    point.cpp
)

I'm importing point.h in my main.cpp file with #include "core/point.h" When I run cmake from the build folder no error occurs. Building using make gives me the following error:

fatal error: point.h: No such file or directory
    2 | #include "core/point.h"
      |          ^~~~~~~~~
compilation terminated.