Use :: in GNUmakefile in general.

GNUmakefile

@@ -7,14 +7,14 @@ DIST?=	dist/
 GO?=	go
 
 #
-all: dist/ir-bm25 dist/ir-tfidf
+all:: dist/ir-bm25 dist/ir-tfidf
 	@true
 
-dist/ir-bm25: cmd/ir-bm25/* internal/**
+dist/ir-bm25:: cmd/ir-bm25/* internal/**
 	"${GO}" build -o "${DIST}" ./cmd/ir-bm25
 
-dist/ir-tfidf: cmd/ir-tfidf/* internal/**
+dist/ir-tfidf:: cmd/ir-tfidf/* internal/**
 	"${GO}" build -o "${DIST}" ./cmd/ir-tfidf
 
-clean:
+clean::
 	rm -rf "${DIST}"