makefile: add go files as a prerequisite

Without declaring the go files as a prerequisite
the `make` won't complie the tool's binary with the latest changes.
IOW the fact that the binary exists is enough and it won't rebuild
it again in case of local changes nor new changes pull from u/s

Makefile

@@ -420,29 +420,29 @@ pkg/version/_buildinfo.json: bin/buildhelper
 
 update-buildinfo: pkg/version/_buildinfo.json
 
-bin/buildhelper:
-	@go build -o bin/buildhelper tools/buildhelper/buildhelper.go
+bin/buildhelper: tools/buildhelper/buildhelper.go
+	@go build -o $@ $<
 
-bin/envsubst:
-	@go build -o bin/envsubst tools/envsubst/envsubst.go
+bin/envsubst: tools/envsubst/envsubst.go
+	@go build -o $@ $<
 
-bin/lsplatform:
-	@go build -o bin/lsplatform tools/lsplatform/lsplatform.go
+bin/lsplatform: tools/lsplatform/lsplatform.go
+	@go build -o $@ $<
 
-bin/catkubeletconfmap:
+bin/catkubeletconfmap: tools/catkubeletconfmap/catkubeletconfmap.go
 	LDFLAGS="-static"
-	CGO_ENABLED=0 go build -o bin/catkubeletconfmap -ldflags "$$LDFLAGS" tools/catkubeletconfmap/catkubeletconfmap.go
+	CGO_ENABLED=0 go build -o $@ -ldflags "$$LDFLAGS" $<
 
-bin/watchnrtattr:
-	@go build -o bin/watchnrtattr tools/watchnrtattr/watchnrtattr.go
+bin/watchnrtattr: tools/watchnrtattr/watchnrtattr.go
+	@go build -o $@ $<
 
-bin/mkginkgolabelfilter:
+bin/mkginkgolabelfilter: tools/mkginkgolabelfilter/mkginkgolabelfilter.go
 	LDFLAGS="-static"
-	@go build -o bin/mkginkgolabelfilter -ldflags "$$LDFLAGS" tools/mkginkgolabelfilter/mkginkgolabelfilter.go
+	@go build -o $@ -ldflags "$$LDFLAGS" $<
 
-bin/nrtcacheck: build-tools
+bin/nrtcacheck: build-tools tools/nrtcacheck/nrtcacheck.go
 	LDFLAGS="-s -w" \
-	go build -mod=vendor -o bin/nrtcacheck -ldflags "$$LDFLAGS" -tags "$$GOTAGS" tools/nrtcacheck/nrtcacheck.go
+	go build -mod=vendor -o $@ -ldflags "$$LDFLAGS" -tags "$$GOTAGS" $<
 
 verify-generated: bundle generate
 	@echo "Verifying that all code is committed after updating deps and formatting and generating code"