Add cross-compilation Makefile targets and tar-based releases.

Revamp the build system to be more inline with other Prometheus exporters.
Notably add Darwin and Windows build targets, and add support for releases
using tar files.

tools/vendor/mvdan.cc/unparam/main.go

@@ -0,0 +1,34 @@
+// Copyright (c) 2017, Daniel Martí <mvdan@mvdan.cc>
+// See LICENSE for licensing information
+
+package main // import "mvdan.cc/unparam"
+
+import (
+	"flag"
+	"fmt"
+	"os"
+
+	"mvdan.cc/unparam/check"
+)
+
+var (
+	tests    = flag.Bool("tests", true, "include tests")
+	exported = flag.Bool("exported", false, "inspect exported functions")
+	debug    = flag.Bool("debug", false, "debug prints")
+)
+
+func main() {
+	flag.Usage = func() {
+		fmt.Fprintln(os.Stderr, "usage: unparam [flags] [package ...]")
+		flag.PrintDefaults()
+	}
+	flag.Parse()
+	warns, err := check.UnusedParams(*tests, *exported, *debug, flag.Args()...)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+	for _, warn := range warns {
+		fmt.Println(warn)
+	}
+}