You can set a project's Build attributes under the Build Options node of the Project Attributes dialog. The default values used in this dialog are specified in your Preferences. See also Build System.
Basically, you need to do the following things to use your own makefiles in SNiFF+:
To use your own makefiles:
Start SNiFF+ and open the project for which you want to set up Make Support.
Project Attributes -- Build Options
Check out the Project Description Files (PDFs) of all the projects for which you will be
building targets.
In the Project Tree, checkmark all the projects for which you will be building targets.
Choose Project > Attributes of Checkmarked Projects....
The Group Project Attributes dialog appears.
Select the Build Options node.
You will now set the Make attributes that are the same for all projects.
Enter your Make command in the Make Command field. Use the
Enter the name of the project's default target (described below).