CMake: headers are installed in CMAKE_INSTALL_INCLUDEDIR

which might not be "include"

Author: nim65s

CMakeLists.txt

@@ -297,7 +297,7 @@ add_library(${PROJECT_NAME} SHARED ${${PROJECT_NAME}_SOURCES}
 target_include_directories(
   ${PROJECT_NAME} SYSTEM
   PUBLIC $<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR}/include>
-         $<INSTALL_INTERFACE:include>)
+         $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
 
 modernize_target_link_libraries(
   ${PROJECT_NAME}