Prevent that the cmake variable BACKWARD_INCLUDE_DIRS be infinitely a…

…ppended on successive cmake runs

BackwardConfig.cmake

@@ -68,13 +68,13 @@ if (${STACK_DETAILS_AUTO_DETECT})
 		LIBDL_INCLUDE_DIR LIBDL_LIBRARY)
 
 	if (LIBDW_FOUND)
-		LIST(APPEND BACKWARD_INCLUDE_DIRS ${LIBDW_INCLUDE_DIRS})
+		LIST(APPEND _BACKWARD_INCLUDE_DIRS ${LIBDW_INCLUDE_DIRS})
 		LIST(APPEND BACKWARD_LIBRARIES ${LIBDW_LIBRARIES})
 		set(STACK_DETAILS_DW TRUE)
 		set(STACK_DETAILS_BFD FALSE)
 		set(STACK_DETAILS_BACKTRACE_SYMBOL FALSE)
 	elseif(LIBBFD_FOUND)
-		LIST(APPEND BACKWARD_INCLUDE_DIRS ${LIBBFD_INCLUDE_DIRS})
+		LIST(APPEND _BACKWARD_INCLUDE_DIRS ${LIBBFD_INCLUDE_DIRS})
 		LIST(APPEND BACKWARD_LIBRARIES ${LIBBFD_LIBRARIES})
 		set(STACK_DETAILS_DW FALSE)
 		set(STACK_DETAILS_BFD TRUE)
@@ -114,28 +114,29 @@ foreach(def ${BACKWARD_DEFINITIONS})
 endforeach()
 
 find_path(BACKWARD_INCLUDE_DIR backward.hpp PATHS ${CMAKE_CURRENT_LIST_DIR})
-list(APPEND BACKWARD_INCLUDE_DIRS ${BACKWARD_INCLUDE_DIR})
 
 include(FindPackageHandleStandardArgs)
 find_package_handle_standard_args(Backward
     REQUIRED_VARS
         BACKWARD_INCLUDE_DIR
         BACKWARD_LIBRARIES
 )
+list(APPEND _BACKWARD_INCLUDE_DIRS ${BACKWARD_INCLUDE_DIR})
 
 macro(add_backward target)
-	target_include_directories(${target} PRIVATE ${BACKWARD_INCLUDE_DIRS})
+	target_include_directories(${target} PRIVATE ${_BACKWARD_INCLUDE_DIRS})
 	set_property(TARGET ${target} APPEND PROPERTY COMPILE_DEFINITIONS ${BACKWARD_DEFINITIONS})
 	set_property(TARGET ${target} APPEND PROPERTY LINK_LIBRARIES ${BACKWARD_LIBRARIES})
 endmacro()
+set(BACKWARD_INCLUDE_DIRS ${_BACKWARD_INCLUDE_DIRS} CACHE INTERNAL "_BACKWARD_INCLUDE_DIRS")
 set(BACKWARD_DEFINITIONS ${BACKWARD_DEFINITIONS} CACHE INTERNAL "BACKWARD_DEFINITIONS")
 set(BACKWARD_LIBRARIES ${BACKWARD_LIBRARIES} CACHE INTERNAL "BACKWARD_LIBRARIES")
-mark_as_advanced(BACKWARD_INCLUDE_DIRS BACKWARD_DEFINITIONS BACKWARD_LIBRARIES)
+mark_as_advanced(_BACKWARD_INCLUDE_DIRS BACKWARD_DEFINITIONS BACKWARD_LIBRARIES)
 
 if (NOT TARGET Backward::Backward)
 	add_library(Backward::Backward INTERFACE IMPORTED)
 	set_target_properties(Backward::Backward PROPERTIES
-        INTERFACE_INCLUDE_DIRECTORIES "${BACKWARD_INCLUDE_DIRS}"
+        INTERFACE_INCLUDE_DIRECTORIES "${_BACKWARD_INCLUDE_DIRS}"
         INTERFACE_LINK_LIBRARIES "${BACKWARD_LIBRARIES}"
         INTERFACE_COMPILE_DEFINITIONS "${BACKWARD_DEFINITIONS}"
     )