Pull request: add -ldflags "-s -w" to release smaller binaries

Merge in DNS/dnsproxy from 109-no-debug to master

Closes #109.

Squashed commit of the following:

commit 303b281
Author: 02f <74245651+02f@users.noreply.github.com>
Date:   Tue Nov 10 20:51:25 2020 +0800

    add -ldflags "-s -w" to release smaller binaries

Makefile

@@ -22,7 +22,7 @@ release: check-env-release
 	mkdir -p $(BUILDDIR)
 	cp LICENSE $(BUILDDIR)/
 	cp README.md $(BUILDDIR)/
-	CGO_ENABLED=0 GOOS=$(GOOS) GOARCH=$(GOARCH) go build -mod=vendor -ldflags "-X main.VersionString=$(VERSION)" -o $(BUILDDIR)/$(NAME)$(ext)
+	CGO_ENABLED=0 GOOS=$(GOOS) GOARCH=$(GOARCH) go build -mod=vendor -ldflags "-s -w -X main.VersionString=$(VERSION)" -o $(BUILDDIR)/$(NAME)$(ext)
 	cd $(BASE_BUILDDIR) ; $(archiveCmd)
 
 test:
@@ -40,4 +40,4 @@ check-env-release:
 	@ if [ "$(GOARCH)" = "" ]; then \
 		echo "Environment variable GOOS not set"; \
 		exit 1; \
-	fi
+	fi