runtime: use futexes with 64-bit time on Linux

Linux introduced new syscalls to fix the year 2038 issue.
To still be able to use the old ones, the Kconfig option
COMPAT_32BIT_TIME would be necessary.

Use the new syscall with 64-bit values for futex by default.
Define _ENOSYS for detecting if it's not available.
Add a fallback to use the older syscall in case the new one is
not available, since Go runs on Linux from 2.6.32 on, per
https://go.dev/wiki/MinimumRequirements.

Updates #75133

Change-Id: I65daff0a3d06b55440ff05d8f5a9aa1c07eb201d
GitHub-Last-Rev: 96dd1bd84b
GitHub-Pull-Request: golang/go#75306
Reviewed-on: https://go-review.googlesource.com/c/go/+/701615
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Mark Freeman <markfreeman@google.com>
Reviewed-by: Jorropo <jorropo.pgm@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/runtime/defs_linux_386.go

@@ -9,6 +9,7 @@ const (
 	_EINTR  = 0x4
 	_EAGAIN = 0xb
 	_ENOMEM = 0xc
+	_ENOSYS = 0x26
 
 	_PROT_NONE  = 0x0
 	_PROT_READ  = 0x1
@@ -136,16 +137,30 @@ type fpstate struct {
 	anon0     [48]byte
 }
 
-type timespec struct {
+// The timespec structs and types are defined in Linux in
+// include/uapi/linux/time_types.h and include/uapi/asm-generic/posix_types.h.
+type timespec32 struct {
 	tv_sec  int32
 	tv_nsec int32
 }
 
 //go:nosplit
-func (ts *timespec) setNsec(ns int64) {
+func (ts *timespec32) setNsec(ns int64) {
 	ts.tv_sec = timediv(ns, 1e9, &ts.tv_nsec)
 }
 
+type timespec struct {
+	tv_sec  int64
+	tv_nsec int64
+}
+
+//go:nosplit
+func (ts *timespec) setNsec(ns int64) {
+	var newNS int32
+	ts.tv_sec = int64(timediv(ns, 1e9, &newNS))
+	ts.tv_nsec = int64(newNS)
+}
+
 type timeval struct {
 	tv_sec  int32
 	tv_usec int32
@@ -223,8 +238,8 @@ type ucontext struct {
 }
 
 type itimerspec struct {
-	it_interval timespec
-	it_value    timespec
+	it_interval timespec32
+	it_value    timespec32
 }
 
 type itimerval struct {