fixed win build (#1654)

metrics/cpu_windows.go

@@ -23,3 +23,8 @@ import (
 func getRUsage(p *process.Process) (inBlock, outBlocks, nvcsw, nivcsw int64) {
 	return 0, 0, 0, 0
 }
+
+// getProcessCPUTime retrieves the process' CPU time since program startup.
+func getProcessCPUTime() int64 {
+	0
+}