If you want the brick bonding to look continuous along the whole length, you are going to have to remove the alternate half-bricks at the existing end within the bond to create a dog-tooth - that would bond it really well as you construct the new wall. Otherwise, why both? - just start the new wall about 10mm away from the existing. You could masonry drill into the middle of the existing end wall enough to insert and mortar-in a brick-tie every 4 or so courses, to physically link the old and new should you so desire.