Variable is set through set_property.

CMakeLists.txt

@@ -40,8 +40,6 @@ include(FetchContent)
 # Test from FileParse should not be visible here
 set(BUILD_FileParse_tests OFF CACHE BOOL "Build FileParse tests" FORCE)
 
-set(some_variable "test" CACHE INTERNAL "Some variable for subprojects")
-
 FetchContent_Declare(
     FileParse
     GIT_REPOSITORY https://github.com/LBNL-ETA/FileParse.git
@@ -69,4 +67,4 @@ if(BUILD_BSDFXMLParser_Tests)
     # Add the test with the specified arguments
     add_test(NAME BSDFXMLParser-test
              COMMAND ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/BSDFXMLParser-test --gtest_catch_exceptions=0)
-endif()
+endif()

src/CMakeLists.txt

@@ -12,6 +12,9 @@ add_library( ${LIB_NAME}
 target_link_libraries(${LIB_NAME} PRIVATE xmlParser)
 target_link_libraries(${LIB_NAME} PRIVATE FileParse)
 
+# Set a property on the existing target
+set_property(TARGET ${LIB_NAME} PROPERTY variable_name "test")
+
 if(NOT "${fPIC}")
   set(fPIC ON)
 endif()