Writing a more advanced Makefile
In the previous recipe, we wrote a basic Makefile without using any of its more advanced features. In this recipe, however, we will write a more advanced Makefile, using object files, more variables, dependencies, and other fancy things.
Here, we will create a new program. The program will calculate the area of three different objects: circles, triangles, and rectangles. Each calculation will be performed in its own function, and every function will reside in its own file. On top of that, we will have a function in a separate file for the help text. There will also be a header file that holds all of the function prototypes.
This project will consist of a total of seven files. If you want, you can choose to download all the files from the directory at https://github.com/PacktPublishing/Linux-System-Programming-Techniques/tree/master/ch3/area.
Since we will create a Makefile for this project, I really recommend that you place...