Newer autoconf versions drastically change the configure script

[kmk3]

(Forked from #4594)

@reinerh commented on Oct 6:

I didn't rebuild configure, as I have a different autoconf version
installed and it would only blow up the diff. If someone wants to test it,
please run autoreconf -vfi before.

Autoconf 2.70/2.71 drastically changed the output, but I have managed to work
around that on Artix previously:

1. Get older PKGBUILD version for autoconf (one that uses autoconf v2.69)
2. Add a few patches from Debian
3. Build and use that

The result generates a configure script that is identical to the committed one.

Misc: I did this for a WIP branch that refactors a bit of configure.ac. I also
thought about putting that PKGBUILD in the AUR, but didn't get around to it.

I think that if you install v2.69 from Debian it should have identical output
as well. Since autoconf by design has virtually no dependencies, it should be
possible to just download the .deb from the archives and install only that.

(In my humble opinion generated files like configure should anyway not be
part of the repository.)

Indeed traditionally it has only been part of the dist tarball. I thought that
this wasn't the case on GitHub, but I checked a few projects that I know use
autoconf and in fact most of them actually don't have the configure script
committed.

I had also thought that one issue could be that by default GitHub would
generate the release tarballs with exactly what is committed (so no extra
files), but from what I'm seeing now it doesn't generate anything, all files
have to be uploaded manually it seems.

One use case that I can think of is if you want to download a zip of the
current version (or of a given commit) with a pre-generated configure script
but without using git.

Note: I don't necessarily think that it should be removed, I'm just sharing
some thoughts.

Cc: @glitsj16 @netblue30