How can I move this water supply line so that I can frame a wall?
Either make the bathroom 2&quot; smaller or 2&quot; bigger.
If you are committed to moving the line then use a hammer drill to put a hole where you want and reroute the water main from the outside in (this will require you to dig outside, cut the line, and install a new line).  If you go this route then I recommend installing PEX as that will be easier to work with (well, easier for me anyway).
I would not recommend trying to make the current hole bigger and push the current line out of the way.  This puts it under tension and increases the risk of it breaking.  Galvanized pipe gets brittle with age, so it loses what little flexibility it ever had and you run the risk of cutting the line while expanding the hole.
###EDIT###
I just took another look at your photo.  Don't know why I thought that was a galvanized pipe.  Looks like PEX to me.  I still recommend against expanding the hole and putting the pipe under tension.
###EDIT 2###
The updated photos and detail helps.  Thanks for the updates.  I didn't realize this was coming through the floor.  Here's my recommendation.  These are not load bearing walls, so I would either keep the framing and plumbing as is, but not take the corner framing all the way to the floor (as others have suggested).  Just notch out the bottom.  Or, get rid of that elbow and run the PEX straight from the floor to the ceiling (I assume it goes there anyway, but it's your call).
Personally, I think your best bet is to do as little as possible with the plumbing and work around it by notching your bottom board.  This will allow future access when things break.