The installation tries to add the BUILTIN\BUILTIN access inside SSRS but fails, due to it might already be there.
Solution:
Enable inheritance on the folder: System Center\Service Manager inside SSRS before running installation. This should remove BUILTIN\BUILTIN and will be readded by the installation.
See blog post:https://blog.jhnr.ch/2016/11/08/error-when-installing-service-manager-data-warehouse-management-server-the-user-or-group-name-builtinbuiltin-is-not-recognized/
