fix(Makefile): fix broken cross binary build

Makefile

@@ -4,8 +4,6 @@ SHORT_NAME      ?= tiller
 
 # go option
 GO        ?= go
-GOARCH    ?= $(shell go env GOARCH)
-GOOS      ?= $(shell go env GOOS)
 PKG       := $(shell glide novendor)
 TAGS      :=
 TESTS     := .
@@ -30,11 +28,10 @@ check-docker:
 	fi
 
 .PHONY: docker-binary
-docker-binary: GOOS = linux
-docker-binary: GOARCH = amd64
-docker-binary: BINDIR = $(CURDIR)/rootfs
+docker-binary: BINDIR = ./rootfs
 docker-binary: GOFLAGS += -a -installsuffix cgo
-docker-binary: build
+docker-binary:
+	GOOS=linux GOARCH=amd64 CGO_ENABLED=0 $(GO) build -o $(BINDIR)/tiller $(GOFLAGS) -tags '$(TAGS)' -ldflags '$(LDFLAGS)' github.com/kubernetes/helm/cmd/tiller
 
 .PHONY: docker-build
 docker-build: check-docker docker-binary
@@ -58,6 +55,7 @@ test-style:
 .PHONY: clean
 clean:
 	@rm -rf $(BINDIR)
+	@rm ./rootfs/tiller
 
 .PHONY: coverage
 coverage: