runtime: don't define CLOCK_REALTIME in os_hurd.go

It's already defined in sysinfo.go.

Patch by Samuel Thibault.

Fixes https://gcc.gnu.org/PR92861

Change-Id: If56519d81d451249d4c854a20b2b89bd7cabcc5a
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/210538
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/libgo/go/runtime/os_hurd.go b/libgo/go/runtime/os_hurd.go
index fab1774..bb3e7ff 100644
--- a/libgo/go/runtime/os_hurd.go
+++ b/libgo/go/runtime/os_hurd.go
@@ -125,7 +125,3 @@
 		physPageSize = uintptr(getPageSize())
 	}
 }
-
-const (
-	_CLOCK_REALTIME = 0
-)