What are the advantages of hiring someone who’s generally skilled, rather than requiring a specific skill set?

Well, sometimes it benifits as the person with wide knowledge of more than one field can do work with many fields with little or no training.

While a person having knowledge of specific field performs best in his/her field, but if they have to change it, it causes problems.

I do agree with the statement generally but my focus would be more that we need to have an individual who has the right attitude rather than a specific skill . Technology always changes - attitude does not

In my opinion this is truly the age of people who are "Jack of all trades but master at none", in a good way though. 

With the kind of environment that we are in and companies becoming smaller and smaller one needs people who are good at many things however might not be experts in that domain.

There is one catch though, if the role requires a specific skill set and you need the person hiring to hit the ground running then you would better go with the specific skilled person. 

With generally skilled you get that flexibility and you can get more value for the money invested onto them.

It mostly depends on the position you are hiring for and what responsibilities the person will have. If you hire tech support, desktop support, security analyst or system administrator for example then its better to have generalist as all of those roles require knowledge of various things but you don't have to necessarily be an expert in each area, perhaps they can work with the vendor directly for some higher-level issue. On the other hand, if you need Digital Forensic Examiner you better hire someone with very specific and tailored expert knowledge. 

Technology changes a lot so if you are an expert in a single area, your skills might be obsolete in 2-3 years. If you hire a generalist you can tailor and grow that person to different areas, depending on the needs of the organization.

Ideally, you should not be hiring one vs the other type, it all depends on the needs of the organization and the role.

I tend to hire people with a really good and broad general skillset, for most roles; the fact that they can be VERY good generalists and "Jack of all trades" usually means that they can be trained to be very good, and sometimes extraordinarily good in certain positions.  Where this is NOT true, is in certain kinds of roles that absolutely require 1 in 100,00 type talent.  I have tried to train upwards of 70 people in IT troubleshooting skills, and after 20 years of trying, my conclusion is that some people just have an innate ability to root out solutions, better than others.

Talent is talent, and cannot be trained past a certain point.  Can you take someone and train them to be extremely competent in certain roles?  Yes.  But we need those with a genuine gift at the tip of the spear.