How to convert an Eclipse managed cdt project into Makefiles

I have a managed C project developed on Eclipse and I would like to convert this project into Makefiles.

I found the Makefiles already generated by Eclipse in debug folder but I saw a warning in the file saying that I should not edit this file.

How can I convert my project easily? I don't want to start from the scratch. It would be perfect if I start it by modifying already generated Makefiles.

My build settings are:

Properties -> Builders
- CDT Builder (ticked)
- Scanner Configuration Builder (ticked)
Properties -> C/C++ Build -> Tool Chain Editor -> Current toolchain: Linux GCC
Properties -> C/C++ Build -> Tool Chain Editor -> Current builder: GNU Make Builder

Solution

I've never tried it, but in principle it should be as simple as making a copy of the generated makefile under another name (typically, makefile or Makefile), and making a few changes in Project Properties -> C/C++ Build:

Under "Builder type", change "Internal builder" to "External builder" (if it isn't that already)
Uncheck "Generate Makefile automatically"
Make sure the "Build directory" is the directory containing your makefile
If you want, you can also customize the name of the target in the "Behaviour" tab