atomicfile: don't Chmod on windows

Not supported.

atomicfile/atomicfile.go

@@ -12,6 +12,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"runtime"
 )
 
 // WriteFile writes data to filename+some suffix, then renames it
@@ -31,9 +32,11 @@ func WriteFile(filename string, data []byte, perm os.FileMode) (err error) {
 	if _, err := f.Write(data); err != nil {
 		return err
 	}
+	if runtime.GOOS != "windows" {
 		if err := f.Chmod(perm); err != nil {
 			return err
 		}
+	}
 	if err := f.Sync(); err != nil {
 		return err
 	}