Subdirectories and Makefiles

The simplest way is to do:

CODE_DIR = code

.PHONY: project_code

project_code:
       $(MAKE) -C $(CODE_DIR)

The .PHONY rule means that project_code is not a file that needs to be built, and the -C flag indicates a change in directory (equivalent to running cd code before calling make). You can use the same approach for calling other targets in the code Makefile.

For example:

clean:
       $(MAKE) -C $(CODE_DIR) clean