Add support for building windows ooni.exe

Gopkg.lock

@@ -89,7 +89,7 @@
   branch = "master"
   name = "github.com/measurement-kit/go-measurement-kit"
   packages = ["."]
-  revision = "cbf1c976aeaa2906f4fda278fc3068f7bde63c47"
+  revision = "0869994e6afcfd1d72f53a4621ce48ed218c3f51"
 
 [[projects]]
   branch = "master"

Makefile

@@ -1,13 +1,18 @@
 GO ?= go
 
 build:
-	@echo "Building ./ooni"
+	@echo "Building dist/ooni"
 	@$(GO) build -i -o dist/ooni cmd/ooni/main.go
 .PHONY: build
 
+build-windows:
+	@echo "Building dist/ooni.exe"
+	CC=x86_64-w64-mingw32-gcc GOOS=windows GOARCH=amd64 CGO_ENABLED=1 go build -o dist/ooni.exe -x cmd/ooni/main.go
+
 update-mk:
 	@echo "updating mk"
 	@dep ensure -update github.com/measurement-kit/go-measurement-kit
+	@test -f vendor/github.com/measurement-kit/go-measurement-kit/libs/ || cd vendor && git submodule add https://github.com/measurement-kit/golang-prebuilt.git github.com/measurement-kit/go-measurement-kit/libs # This is a hack to workaround: https://github.com/golang/dep/issues/1240
 .PHONY: update-mk
 
 bindata: