suppress cgo compiler warnings in build output

Makefile

@@ -2,13 +2,14 @@ PREFIX  ?= /usr/local
 BINDIR  ?= $(PREFIX)/bin
 BINARY  := barnard
 
-GO      ?= go
-GOFLAGS ?=
+GO       ?= go
+GOFLAGS  ?=
+export CGO_CFLAGS += -w -O2
 
 .PHONY: build install uninstall clean fmt vet
 
 build:
-	$(GO) build $(GOFLAGS) -o $(BINARY) .
+	@$(GO) build $(GOFLAGS) -o $(BINARY) .
 
 install: build
 	install -d $(DESTDIR)$(BINDIR)