Ckeck executable dependencies in a Makefile

Makefile

# Check if all executables needed are in the PATH before execite any rule/task.
EXECUTABLES = rm mkdir cp mvn java go	# List of executables
CHECK_EXECUTABLES := $(foreach exec,$(EXECUTABLES),\
        $(if $(shell which $(exec)),some string,$(error "No $(exec) in PATH. Check README.md for build requirements")))

# This must be at the begining of the file, so ASAP make parses the file will fail if some of
# dependencies does not exist