"No debugging symbols found" in gdb after compiling 3D Toolkit on Linux with CMake

I wanted to step through the source code as I execute the 3D Toolkit show program on Linux but the gdb debugger was unable to load debugging symbols, as shown in the screenshot below.

Previously, I compiled the application with the "make" command but by default, it created build instead of debug executables. So I had to enable debug compilation. In order to do that, I had to do the following:

1. Open up the 3D Toolkit's CMakeList.txt file in a text editor.
   
   
   
2. Locate the line
   
   set (CMAKE_BUILD_TYPE "" CACHE INTERNAL "" FORCE)
   
3. Change the above line to the following:
   
   set (CMAKE_BUILD_TYPE "Debug")
   
   
   
4. Now recompile the application.
   

Now, the debugger gdb should be able to load the debug symbols and the source code can be stepped through, as shown below.