CMakeLists: include path fix + compatibility.

Author: aikawayataro

CMakeLists.txt

@@ -195,7 +195,7 @@ install(FILES readme.md
 # Add an interface target to export it
 add_library(RapidJSON INTERFACE)
 
-target_include_directories(RapidJSON INTERFACE $<INSTALL_INTERFACE:include/rapidjson>)
+target_include_directories(RapidJSON INTERFACE $<INSTALL_INTERFACE:include>)
 
 install(DIRECTORY include/rapidjson
     DESTINATION "${INCLUDE_INSTALL_DIR}"

RapidJSONConfig.cmake.in

@@ -17,3 +17,7 @@ get_filename_component(RapidJSON_CMAKE_DIR "${CMAKE_CURRENT_LIST_FILE}" PATH)
 get_target_property(RapidJSON_INCLUDE_DIR RapidJSON INTERFACE_INCLUDE_DIRECTORIES)
 
 set( RapidJSON_INCLUDE_DIRS ${RapidJSON_INCLUDE_DIR} )
+
+if(NOT TARGET rapidjson)
+  add_library(rapidjson ALIAS RapidJSON)
+endif()