Cleanup lchmod logic in archive

Move to single lchmod interface mirroring other implementations.
Separate logic for freebsd which supports symlink no follow flag.

Signed-off-by: Derek McGowan <derek@mcg.dev>

archive/tar_mostunix.go

@@ -18,7 +18,11 @@
 
 package archive
 
-import "golang.org/x/sys/unix"
+import (
+	"os"
+
+	"golang.org/x/sys/unix"
+)
 
 // mknod wraps Unix.Mknod and casts dev to int
 func mknod(path string, mode uint32, dev uint64) error {
@@ -34,3 +38,18 @@ func lsetxattrCreate(link string, attr string, data []byte) error {
 	}
 	return err
 }
+
+// lchmod checks for symlink and changes the mode if not a symlink
+func lchmod(path string, mode os.FileMode) error {
+	fi, err := os.Lstat(path)
+	if err != nil {
+		return err
+	}
+
+	if fi.Mode()&os.ModeSymlink == 0 {
+		if err := os.Chmod(path, mode); err != nil {
+			return err
+		}
+	}
+	return nil
+}