Fix Makefile build cmd to create static binaries

The previous build command produces dynamic executables
instead of the intended (but not well noted in the Makefile)
static executables. This commit includes changes noted in
upstream `golang/go` issues which appear to work as intended
for others.

- refs GH-94
- refs golang/go#38789
- refs golang/go#26492

Makefile

@@ -42,7 +42,7 @@ VERSION 				= $(shell git describe --always --long --dirty)
 
 # The default `go build` process embeds debugging information. Building
 # without that debugging information reduces the binary size by around 28%.
-BUILDCMD				=	go build -mod=vendor -a -ldflags="-s -w -X $(VERSION_VAR_PKG).version=$(VERSION)"
+BUILDCMD				=	go build -mod=vendor -tags 'osusergo netgo' -a -ldflags "-extldflags '-static' -s -w -X $(VERSION_VAR_PKG).version=$(VERSION)"
 GOCLEANCMD				=	go clean -mod=vendor ./...
 GITCLEANCMD				= 	git clean -xfd
 CHECKSUMCMD				=	sha256sum -b