Include Makefile in another Makefile only if exists

This snippet allows you to include the contents of a Makefile located in a folder in the root Makefile.

MAKEFILE_FOLDER := ./vendor/FOLDER THAT CONTAINS MAKEFILE

exist := $(wildcard $(MAKEFILE_FOLDER)/Makefile)
ifneq ($(strip $(exist)),)
  include $(MAKEFILE_FOLDER)/Makefile
endif

Alternative :

DIR_TO_CHECK_FOR = 'large_directory'

download_data:
    ifeq ("$(wildcard $(DIR_TO_CHECK_FOR))", "")
        @echo "Directory does not exist."
        # Perform download...
    else
        @echo "Skipping download because directory already exists."
    endif

Sources:

• http://www.magpar.net/static/magpar/doc/html/makefiles.html
• https://github.com/naegelyd/til/blob/master/misc/check-if-directory-exists-in-makefile.md