Makefile: Statically building the binary to not depend on gcc compiler (#59)

This is to statically build the cmk binary. It means it doesn't depend on gcc being present to work. The use case is that the cmk binary without this won't work in any alpine docker image.

Author: khos2ow

Makefile

@@ -26,7 +26,7 @@ PKGS     = $(or $(PKG),$(shell $(GO) list ./... | grep -v "^$(PACKAGE)/vendor/")
 TESTPKGS = $(shell $(GO) list -f '{{ if or .TestGoFiles .XTestGoFiles }}{{ .ImportPath }}{{ end }}' $(PKGS))
 GIT_SHA  = $(shell git rev-parse --short HEAD)
 
-GO      = go
+GO      = CGO_ENABLED=0 go
 GODOC   = godoc
 GOFMT   = gofmt
 TIMEOUT = 15