Equals sign seems unnecessarily escaped

In rubygems, we sometimes print quite complicated commands when building extensions fail, so that the user can try to rerun things and reproduce the problem. I noticed that equal signs are escaped, making things a bit more overwhelming.

I think there might be a reason for it that I don't know of, or some shell where it's necessary, but I checked the equivalent python package, and it does not escape them, so maybe it can be changed.

➜  ~ python -c 'import shlex; print(shlex.join(["FOO=BAR", "baz"]))'
FOO=BAR baz

➜  ~ ruby -rshellwords -e 'puts Shellwords.join(["FOO=BAR", "bar"])'
FOO\=BAR baz

If the change is accepted, I can work on it.

Comienza en el punto de entrada Shellwords.join mostrado en el issue y sigue cómo se escapan las palabras de comando que contienen signos de igual. Comprueba el comportamiento existente de seguridad del shell antes de decidir si la salida puede coincidir con el ejemplo de Python y, después, verifica que los signos de igual se gestionen como se espera sin introducir regresiones en otros casos de escape.