Use configure_file for Perl files

[mpflanzer]

Solves the problem that the creduce executable was not regenerated
everytime creduce.in changed.

[eeide]

Thank you for this patch! I will review it.

[regehr]

Yes, thanks, this is great. I looked at the changes and see no problems, but my CMake is not strong.

[mpflanzer]

Anything blocking this? I ran cmake with and without my changes and got no difference between the two variants if that helps. ;-)

[eeide]

I am going to make a new release of C-Reduce before I consider this pull request.

[eeide]

I tried this on my Mac this morning. If I tweak creduce.in in my source tree, a make in my build tree does cause creduce to be regenerated. Yay!

But if I just remove creduce from my build tree, a make does not regenerate it.

I guess this is OK, but it is sort of un-make-like dependency behavior.

I am using CMake 3.11.4.

[regehr]

Weird. Anyhow this seems like an improvement and it sounds like we should merge.

[mpflanzer]

Mhh, ok. I'll try to have a look next week. Maybe that can be fixed as well.

[mpflanzer]

At least part of the problem might be a bug in CMake itself. I filed an issue here: https://gitlab.kitware.com/cmake/cmake/issues/18218. I'll keep an eye on it and let you know about it's progress.

Feel free to merge this PR in the meantime if you want. Or we wait until we know more about the outcome of the CMake issue.