Grant plan users read access to the ROBOCORP_HOME base directory

[jherbel]

As of now, only admin users have access to the ROBOCORP_HOME base directory on Windows systems, which is what we want. Furthermore, plan users are granted full access to their user-specific ROBOCORP_HOME directory (which is located inside the base directory). This setup is as desired. However, it turned out that this prevents non-admin plan users from building RCC environments. For some reason, read access to the ROBOCORP_HOME base directory is required. Without it, micromamba crashes:

info     libmamba ****************** Backtrace Start ******************
debug    libmamba Loading configuration
trace    libmamba Compute configurable 'create_base'
trace    libmamba Compute configurable 'no_env'
trace    libmamba Compute configurable 'no_rc'
trace    libmamba Compute configurable 'rc_files'
trace    libmamba Compute configurable 'root_prefix'
trace    libmamba Compute configurable 'envs_dirs'
critical libmamba weakly_canonical: Access is denied.: "C:\rmk\rcc_home\vagrant2\envs"
info     libmamba ****************** Backtrace End ********************