FIX: copyfile()/symlinks on Linux, Matlab < R2020a

[octomike]

I tried running the SPM container on ds000001 which I pulled with datalad. It turns out that datalad is using symbolic links for the images in anat/ and func/ etc pointing to a .git-annex folder two levels above.

Unfortunately, copyfile() on Linux with Matlab <= 2019b does not dereference the file and when SPM is copying a relative symlink to the tmp/output folder, the link breaks.

This PR is checking if we are on Linux on Matlab < 2020a (with an ugly versioncmp hack) and uses system('cp -rL...') instead of copyfile().

Also, as I mention in the comment, it would probably be much nicer to keep the symbolic links for all platforms, but I'm having a hard time coming up with a portable solution for that. And I'm also not entirely sure this is compatible with SPM's behavior (would it modify source files in that case?)

[gllmflndn]

There is now a function spm_copy that could be used in spm_BIDS_App.m. The issue with symbolic links could then be dealt with there (spm_check_version might come handy) or we could just switch to the MATLAB Runtime R2020a as you mention.
It seems safer to make hard copies as sources could be modified.

[octomike]

Okay, cool. So should I just revert the changes and change copyfile() to spm_copy() and leave this here until spm_copy is updated?

[gllmflndn]

Yes, spm_copy is just a wrapper around copyfile but it will also uncompress and move sidecar .json files as well. I will look building a new SPM12 standalone with R2020a that we could use here.