initialPreReleaseIfNotOnPrerelease on gradle command line?

[am312]

This is possible:

./gradlew release -Prelease.versionIncrementer=incrementPrerelease

but how can I accomplish this function in the shell including the RC1 portion?

scmVersion {
  versionIncrementer 'incrementPrerelease', [initialPreReleaseIfNotOnPrerelease: 'RC1']
}

Thanks