It looks like the default build directory in QTCreator 13 has changed from 

../%{JS: Util.asciify("build-%{Project:Name}-%{Kit:FileSystemName}-%{BuildConfig:Name}")}

to 

./build/%{Asciify:%{Kit:FileSystemName}-%{BuildConfig:Name}}

This change is going to really bite and has no apparent benefit except to mess up things for the unwary.  At the least you should draw attention to this significant change in release notes or somewhere.

I'd like to know how I could specify the build directory in CMaakeLists.txt and .pro files so I can override the default setting without having to change instances of QtCreator. 

Please think about the consequences of this change.