How to linearize target vector by PCR
If you use PCR, the products from the reaction will be linear pieces of DNA. Yes, you'll have two templates that are circular after the first denaturation, but when you anneal the primers and perform elongation you'll be making linear fragments. The exponential nature of PCR means that these linear fragments will far exceed the template after several cycles.

PCR can also be tuned to be selective for shorter fragments. If you use the proper protocol for PCR of the entire plasmid, your PCR products will be a complete copy of the plasmid that is linear.