I don't think the first sentence would be correct beacuse it leads me to the meaning that if someone doesn't want to do something then somebody else makes an excuse. the secend sentence seems more acceptable to me.
Additionaly, I have heard this sentence in this way that they say : if someone doesn't want to do something, he/she would make an excuse.
I am not a teacher though, I may be wrong.
Student or Learner