unix: add CloseRange

The close_range(2) syscall is available since Linux kernel v5.9,
with additional functionality of CLOSE_RANGE_CLOEXEC since v5.11.

No tests are required since this is a bare syscall.

Change-Id: I410470e3713e2005cc7acf24d1347938fe05ef63
Reviewed-on: https://go-review.googlesource.com/c/sys/+/301409
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Trust: Emmanuel Odeke <emmanuel@orijtech.com>

unix/linux/types.go

@@ -84,6 +84,7 @@ struct termios2 {
 #include <linux/can/raw.h>
 #include <linux/capability.h>
 #include <linux/cgroupstats.h>
+#include <linux/close_range.h>
 #include <linux/cryptouser.h>
 #include <linux/devlink.h>
 #include <linux/dm-ioctl.h>
@@ -3648,3 +3649,9 @@ type (
 	HIDRawReportDescriptor C.struct_hidraw_report_descriptor
 	HIDRawDevInfo          C.struct_hidraw_devinfo
 )
+
+// close_range
+const (
+	CLOSE_RANGE_UNSHARE = C.CLOSE_RANGE_UNSHARE
+	CLOSE_RANGE_CLOEXEC = C.CLOSE_RANGE_CLOEXEC
+)