Make nightly release support system level install on Windows

[simonhong]

Chrome canary doesn't support system level install on Windows.
And we also set same value.

Should we have same policy for that or enable system level install on Windows?

In setup_main.cc,

  // Make sure system_level is supported if requested. For historical reasons,
  // system-level installs have never been supported for Chrome canary (SxS).
  // This is a brand-specific policy for this particular mode. In general,
  // system-level installation of secondary install modes is fully supported.
  if (!install_static::InstallDetails::Get().supports_system_level() &&
      (system_install ||
       cmd_line.HasSwitch(installer::switches::kSelfDestruct) ||
       cmd_line.HasSwitch(installer::switches::kRemoveChromeRegistration))) {
    return installer::SXS_OPTION_NOT_SUPPORTED;
  }

chromium_install_modes.cc has that config.
CC @bbondy

[simonhong]

@mihaiplesa Because of this setting, our windows nightly stub/standalone installer doesn't work with admin. When we run brave_installer.exe with nightly and system level, it just early returns.
When I run it w/o admin, it works well.
Also, you can build non-admin mode installer by setting TAG_ADMIN env to False.

build_omaha.py handles it.

  tag_admin = os.environ.get('TAG_ADMIN', 'prefers')
  tag = 'appguid=APP_GUID&appname=TAG_APP_NAME&needsadmin=TAG_ADMIN&lang=en&ap=TAG_AP'
  tag = tag.replace("TAG_ADMIN", tag_admin)
  tag = tag.replace("APP_GUID", args.guid[0])
  tag = tag.replace("TAG_APP_NAME", args.tag_app_name[0])
  tag = tag.replace("TAG_AP", args.tag_ap[0])

[bbondy]

I think all code that lands even on master is reviewed so I think it's ok. Is there some reason to disable or treat it different from other channels?
cc @diracdeltas @fmarier

[simonhong]

I can't find the exact reason from the source.
For historical reasons and brand specific policy from the comments are the only reason I can find. :)
I also think supporting admin on nightly would be fine.

[mihaiplesa]

I'd suggest going forward with unblocking this (we can revert if needed).