[#1262] sdnotify: Get rid of go:linkname for nanotime

Signed-off-by: Ekaterina Lebedeva <ekaterina.lebedeva@yadro.com>

pkg/util/sdnotify/clock.go

@@ -1,10 +0,0 @@
-package sdnotify
-
-import (
-	// For go:linkname to work.
-	_ "unsafe"
-)
-
-//go:noescape
-//go:linkname nanotime runtime.nanotime
-func nanotime() int64

pkg/util/sdnotify/clock.s

@@ -1,2 +0,0 @@
-// The file is intentionally empty.
-// It is a workaround for https://github.com/golang/go/issues/15006

pkg/util/sdnotify/sdnotify.go

@@ -6,6 +6,7 @@ import (
 	"net"
 	"os"
 	"strings"
+	"time"
 )
 
 const (
@@ -16,6 +17,7 @@ const (
 
 var (
 	socket *net.UnixAddr
+	start  = time.Now()
 
 	errSocketVariableIsNotPresent = errors.New("\"NOTIFY_SOCKET\" environment variable is not present")
 	errSocketIsNotInitialized     = errors.New("socket is not initialized")
@@ -51,7 +53,7 @@ func FlagAndStatus(status string) error {
 		//    must be sent, containing "READY=1".
 		//
 		// For MONOTONIC_USEC format refer to https://www.man7.org/linux/man-pages/man3/sd_notify.3.html
-		status += fmt.Sprintf("\nMONOTONIC_USEC=%d", uint64(nanotime())/1e3 /* microseconds in nanoseconds */)
+		status += fmt.Sprintf("\nMONOTONIC_USEC=%d", uint64(time.Since(start))/1e3 /* microseconds in nanoseconds */)
 	}
 	status += "\nSTATUS=" + strings.TrimSuffix(status, "=1")
 	return Send(status)