cmake_minimum_required(VERSION 3.14)
enable_language(C)

add_library(foo1 STATIC empty.c)
target_include_directories(foo1 PUBLIC include)
target_link_libraries(foo1 PRIVATE foo2 foo3 foo4)

add_library(foo2 STATIC empty.c)
target_include_directories(foo2 PUBLIC $<TARGET_PROPERTY:foo1,INCLUDE_DIRECTORIES>)

add_library(foo3 STATIC empty.c)
target_include_directories(foo3 PUBLIC $<TARGET_PROPERTY:foo2,INCLUDE_DIRECTORIES>)

add_library(foo4 STATIC empty.c)
target_include_directories(foo4 PUBLIC $<TARGET_PROPERTY:foo3,INCLUDE_DIRECTORIES>)

# Evaluate a genex that looks up INCLUDE_DIRECTORIES on multiple targets.
file(GENERATE OUTPUT out.txt CONTENT "$<TARGET_PROPERTY:foo4,INCLUDE_DIRECTORIES>")