unix: remove StTimespec type on AIX

On AIX, Stat_t's fields dealing with time are of type StTimespec while
all other GOOS are using Timespec.
StTimespec and Timespec are the same on ppc but not in ppc64. Therefore,
values returned by ppc64 syscalls need to be adjusted in order to
allow the use of Timespec instead of StTimespec.

Fixes golang/go#32073

Change-Id: I0c212bf1741a27c49e995bf928d4941b6d583e54
Reviewed-on: https://go-review.googlesource.com/c/sys/+/177838
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

unix/syscall_aix_ppc64.go

@@ -32,3 +32,50 @@ func (msghdr *Msghdr) SetControllen(length int) {
 func (cmsg *Cmsghdr) SetLen(length int) {
 	cmsg.Len = uint32(length)
 }
+
+// In order to only have Timespec structure, type of Stat_t's fields
+// Atim, Mtim and Ctim is changed from StTimespec to Timespec during
+// ztypes generation.
+// On ppc64, Timespec.Nsec is an int64 while StTimespec.Nsec is an
+// int32, so the fields' value must be modified.
+func fixStatTimFields(stat *Stat_t) {
+	stat.Atim.Nsec >>= 32
+	stat.Mtim.Nsec >>= 32
+	stat.Ctim.Nsec >>= 32
+}
+
+func Fstat(fd int, stat *Stat_t) error {
+	err := fstat(fd, stat)
+	if err != nil {
+		return err
+	}
+	fixStatTimFields(stat)
+	return nil
+}
+
+func Fstatat(dirfd int, path string, stat *Stat_t, flags int) error {
+	err := fstatat(dirfd, path, stat, flags)
+	if err != nil {
+		return err
+	}
+	fixStatTimFields(stat)
+	return nil
+}
+
+func Lstat(path string, stat *Stat_t) error {
+	err := lstat(path, stat)
+	if err != nil {
+		return err
+	}
+	fixStatTimFields(stat)
+	return nil
+}
+
+func Stat(path string, statptr *Stat_t) error {
+	err := stat(path, statptr)
+	if err != nil {
+		return err
+	}
+	fixStatTimFields(statptr)
+	return nil
+}