mk: merge checkfmt into lint

No need to have two separate targets.

Signed-off-by: Robin Jarry <robin@jarry.cc>

.builds/alpine-edge.yml

@@ -11,9 +11,6 @@ environment:
   DESTDIR: ./out
   GOFLAGS: "-tags=notmuch"
 tasks:
-  - checkfmt: |
-      cd aerc
-      make checkfmt
   - lint: |
       cd aerc
       make lint

Makefile

@@ -56,16 +56,13 @@ dev:
 fmt:
 	gofmt -w .
 
-.PHONY: checkfmt
-checkfmt:
-	@if [ `gofmt -l . | wc -l` -ne 0 ]; then \
+.PHONY: lint
+lint:
+	@echo "gofmt -d ."; if [ `gofmt -l . | wc -l` -ne 0 ]; then \
 		gofmt -d .; \
 		echo "ERROR: source files need reformatting with gofmt"; \
 		exit 1; \
 	fi
-
-.PHONY: lint
-lint:
 	$(GO) vet ./...
 
 .PHONY: tests