:beetle: Fix syntax error

Make does not like spaces. It want real tabs.

makefile

@@ -9,10 +9,10 @@ PANDOC_GEN := pandoc --standalone --wrap=none --template src/templates/main.html
 
 .PHONY: build
 build: $(GEN_FILES)
-    $(info HTML generated)
+	$(info HTML generated)
 
 %.gen.html: %.src.html %.src.md
-    $(PANDOC_GEN) --output $@ $<
+	$(PANDOC_GEN) --output $@ $<
 
 .PHONY: clean
 clean: