\file_compare_timestamp:nNnTF doesn't work with lualatex

[u-fischer]

\documentclass[12pt]{article}

\begin{document}
\ExplSyntaxOn
\file_compare_timestamp:nNnTF{article.cls}>{report.cls}{yes}{no}

\ExplSyntaxOff
\end{document}

gives

! Undefined control sequence.
<argument> \LaTeX3 error: 
                Primitive \(pdf)filemoddatenot available
l.16 ...re_timestamp:nNnTF{article.cls}>{report.cls}
                                                  {yes}{no}
? x

The reason is that l3file.dtx actively disables it if \tex_filemoddate:D is not defined:

\cs_if_exist:NF \tex_filemoddate:D
  {
    \prg_set_conditional:Npnn \file_compare_timestamp:nNn #1#2#3
      { p , T , F , TF }
      {
        \__kernel_msg_expandable_error:nnn
          { kernel } { primitive-not-available }
          { \(pdf)filemoddate }
        \prg_return_false:
      }
  }