Jenkins: Build job with dependency to other artifact/project
In your case as you want to use different Jobs for Core and Project, the gradle settings projectDir doesn't meet the path structure with respective to Jenkins workspaces if you use as is which comes by Jenkins default workspace management.
Use Custom Workspace, which helps this to point to the folder where you have setup a folder similar to the Dev folder structure.
Ex:Create root folder to hold the Core and Projects and assuming that you are running Jenkins (/var/lib/jenkins/workspace/code)
Code
-core
--src/
--build.gradle
--settings.gradle
-project
--src/
--build.gradle
--settings.gradle
Use the custom workspace for core job as /var/lib/jenkins/workspace/code/core
and for the project job use the custom workspace as /var/lib/jenkins/workspace/code/project