os, syscall: implement Stat and Lstat

File.Stat is left as a stub for now.

Tests are a bit stubbed down because os.ReadDir, os.Symlink, and t.TempDir are not yet (fully) implemented.
TODO: reimport tests from upstream as those materialize.

src/os/stat_unix.go

@@ -0,0 +1,42 @@
+// +build darwin linux,!baremetal
+
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package os
+
+import (
+	"syscall"
+)
+
+// Sync is a stub, not yet implemented
+func (f *File) Sync() error {
+	return ErrNotImplemented
+}
+
+// statNolog stats a file with no test logging.
+func statNolog(name string) (FileInfo, error) {
+	var fs fileStat
+	err := ignoringEINTR(func() error {
+		return syscall.Stat(name, &fs.sys)
+	})
+	if err != nil {
+		return nil, &PathError{Op: "stat", Path: name, Err: err}
+	}
+	fillFileStatFromSys(&fs, name)
+	return &fs, nil
+}
+
+// lstatNolog lstats a file with no test logging.
+func lstatNolog(name string) (FileInfo, error) {
+	var fs fileStat
+	err := ignoringEINTR(func() error {
+		return syscall.Lstat(name, &fs.sys)
+	})
+	if err != nil {
+		return nil, &PathError{Op: "lstat", Path: name, Err: err}
+	}
+	fillFileStatFromSys(&fs, name)
+	return &fs, nil
+}