In your deploy project:
- Configure a Promoted Build Parameter named (for example) PromotedBuild
- Configure Copy artifacts from another project to Specific build with Build number as ${PromotedBuild_NUMBER}
Also, if you want to trigger the deploy project from your build project, you can do this:
- In your promotion process of your build project add Trigger parameterized build on other projects with a Predefined parameter of PromotedBuild_NUMBER=$PROMOTED_NUMBER.