Makefile - download jokes only once

Makefile

@@ -5,10 +5,10 @@ DST_IMAGES := $(sort $(addprefix build/,$(addsuffix .bmp,$(notdir $(basename $(S
 
 all: clean build
 
-download: jokes.json
+download: build/jokes.json
 
-jokes.json: build-dir
-	curl -o build/jokes.json https://github.com/wiz64/superfun/raw/main/database/ichd/jokes-file.json
+build/jokes.json: build-dir
+	[ -e build/jokes.json ] || curl -o build/jokes.json https://github.com/wiz64/superfun/raw/main/database/ichd/jokes-file.json
 
 build: build-dir images download