Related to https://github.com/dotnet/release/issues/1707

We should consider defaulting to RTM branding not just in the YML files (as done for 10.0 GA), but also in the build entry-point. This would ensure that the default experience when building from a release branch is an RTM build. However, RTM branding should not be the default for repo builds, to avoid unintentionally generating stable packages.