executor/linux: comment this bizarre code

drivers/shared/executor/executor_linux.go

@@ -163,7 +163,10 @@ func (l *LibcontainerExecutor) Launch(command *ExecCommand) (*ProcessState, erro
 	}
 
 	// Turn relative-to-chroot path into absolute path to avoid
-	// libcontainer trying to resolve the binary using $PATH
+	// libcontainer trying to resolve the binary using $PATH.
+	// Do *not* use filepath.Join as it will translate ".."s returned by
+	// filepath.Rel. Prepending "/" will cause the path to be rooted in the
+	// chroot which is the desired behavior.
 	path = "/" + rel
 
 	combined := append([]string{path}, command.Args...)