Hey Francisco,
Tito is right there is no image aspect ratio squeeze, but you can assign an editor to LR. So if you assign PS then edit will take you into PS where you can run a macro then when you shut PS down it takes you back to LR. Of course it doesnt have to be PS it can be any image editor.
I've looked into this before, and Lightroom has nothing like Pixel Aspect Ratio. Nothing that can help anamorphic shooters. I grade my stills there, and then de-stretch in PS...