Auto merge of #1943 - mseri:patch-1, r=alexcrichton

It maybe a tacky way, but I think that changing `util::without_prefix` is a bad approach. Maybe modify `process.build_command` could be another possible approach.

It could be worth to take more time to be sure to find the root of the problem. I am quite new to rust, if anybody can point out the right way of dealing with it, I will be happy to submit a new PR.