Insiro o comando e me retorna esta mensagem:
Versão do Ruby:
$ ruby -v
ruby 2.4.4p296 (2018-03-28 revision 63013) [x64-mingw32]
Problema:
sass --watch estilos.scss estilos.css
Could not find an option named "watch".
Usage: sass <input> [output]
--[no-]stdin Read the stylesheet from stdin.
--[no-]indented Use the indented syntax for input from stdin.
-I, --load-path=<PATH> A path to use when resolving imports.
May be passed multiple times.
-s, --style=<NAME> Output style.
[expanded (default), compressed]
-c, --[no-]color Whether to emit terminal colors.
-q, --[no-]quiet Don't print warnings.
--[no-]trace Print full Dart stack traces for exceptions.
-h, --help Print this usage information.
--version Print the version of Dart Sass.