I added the following to build.sbt and it worked fine.
com.github.retronym.SbtOneJar.oneJarSettings
artifact in (Compile, oneJar) ~= { art =>
art.copy(`classifier` = Some("one-jar"))
}
addArtifact(artifact in (Compile, oneJar), oneJar)
and then
sbt publish
Published the jar to Artifactory.