You won't. The only time you get extra copies is if it is specified on the Store page. For example, if you purchase Frozen Synapse you get two copies. One goes in your Library, the other one gets put into your Inventory to be used as a gift.

For something like this, the winner would only get the game that they don't already have. If they have Hotline 1, they only get Hotline 2. It's like if you bought a Bundle in the Steam Store. Let's use the Serious Sam Complete Pack for an example. Whatever games you already have, you will not get a second copy of, and it will work the same with game packs like the one you are giving away.