Invoke Go consistently and remove GO15VENDOREXPERIMENT from container

Makefile

@@ -94,7 +94,7 @@ shell: $(SCOPE_BACKEND_BUILD_UPTODATE)
 	/bin/bash
 
 tests: $(SCOPE_BACKEND_BUILD_UPTODATE)
-	./tools/test -no-go-get
+	env -u GOGC $(GO_ENVS) ./tools/test -no-go-get
 
 lint: $(SCOPE_BACKEND_BUILD_UPTODATE)
 	./tools/lint .

backend/Dockerfile

@@ -1,5 +1,4 @@
 FROM golang:1.6.0
-ENV GO15VENDOREXPERIMENT 1
 RUN apt-get update && apt-get install -y libpcap-dev python-requests time
 RUN go clean -i net && go install -tags netgo std &&  go install -race -tags netgo std
 RUN go get -tags netgo \

experimental/Makefile

@@ -4,7 +4,7 @@ DIRS=$(shell find . -maxdepth 2 -name *.go | xargs -n1 dirname | sort -u)
 TARGETS=$(join $(patsubst %,%/,$(DIRS)),$(patsubst ./%,%,$(DIRS)))
 BUILD_IN_CONTAINER=true
 RM=--rm
-
+GO ?= env GO15VENDOREXPERIMENT=1 GOGC=off go
 all: $(TARGETS)
 
 ifeq ($(BUILD_IN_CONTAINER),true)
@@ -13,11 +13,11 @@ $(TARGETS):
 		weaveworks/scope-backend-build -C experimental $@
 else
 $(TARGETS):
-	go build -ldflags "-extldflags \"-static\"" -tags netgo -o $@ ./$(@D)
+	$(GO) build -ldflags "-extldflags \"-static\"" -tags netgo -o $@ ./$(@D)
 endif
 
 test:
-	go test ./...
+	env -u GOGC $(GO) test ./...
 
 clean:
-	go clean ./...
+	$(GO) clean ./...