Demo of target_include_directories(... INTERFACE ...)

CMakeLists.txt

cmake_minimum_required(VERSION 3.0)
project(x)

file(WRITE "${CMAKE_CURRENT_SOURCE_DIR}/include/fonts.hpp"
     "#include <iostream>\ninline int Print() { std::cout << \"Running.\\n\"; return 0; }\n")
file(WRITE "${CMAKE_CURRENT_SOURCE_DIR}/test/main.cpp"
     "#include \"fonts.hpp\"\nint main() { return Print(); }\n")

add_library(Fonts INTERFACE)
target_include_directories(Fonts INTERFACE "${CMAKE_CURRENT_SOURCE_DIR}/include")

add_executable(FontsTest test/main.cpp)
target_link_libraries(FontsTest Fonts)