I need to perform some updates on files within my project (our the output of my project) and I need to do this before the deployment package (zip file) is produced.
Is there a build target that fires between the build and packaging phases?
No, there is no “BeforePackage” build target. You can use AfterCompile target. A little bit more hacky will be to use GenerateDocumentation target for your purposes, it will come before packaging if no one has overriden ordering of targets.