FIX: separated situation of building/installing on target_include_directories on cmake

SEE:	https://github.com/godotengine/godot-cpp/pull/1966

 Changes to be committed:
	- modified:   cmake/godotcpp.cmake

cmake/godotcpp.cmake

@@ -371,7 +371,9 @@ function(godotcpp_generate)
     target_include_directories(
         godot-cpp
         ${GODOTCPP_SYSTEM_HEADERS_ATTRIBUTE}
-        PUBLIC include ${CMAKE_CURRENT_BINARY_DIR}/gen/include
+        PUBLIC
+            $<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR}/gen/include>
+            $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
     )
 
     # gersemi: off