Add cdp support for xpath scrapers (#625)

Co-authored-by: WithoutPants <53250216+WithoutPants@users.noreply.github.com>

vendor/github.com/knq/sysutil/sysutil_linux.go

@@ -0,0 +1,36 @@
+// +build linux
+
+package sysutil
+
+import (
+	"bytes"
+	"io/ioutil"
+	"strconv"
+	"time"
+)
+
+var (
+	btimePrefix = []byte("btime ")
+	lineEnd     = []byte("\n")
+)
+
+func init() {
+	buf, err := ioutil.ReadFile("/proc/stat")
+	if err != nil {
+		btime = time.Now()
+		return
+	}
+
+	for _, line := range bytes.SplitN(buf, lineEnd, -1) {
+		if bytes.HasPrefix(line, btimePrefix) {
+			t, err := strconv.ParseInt(string(line[len(btimePrefix):]), 10, 64)
+			if err != nil {
+				btime = time.Now()
+				return
+			}
+
+			btime = time.Unix(t, 0)
+			break
+		}
+	}
+}