Library generation fails on AFS because AFS does not support hard links across directories

[magv]

Hi, all. It seems pySecDec library generation does not work on the AFS file system. With pySecDec 1.6.4 if I run python3 generate_easy.py from examples/easy, I get this error:

Traceback (most recent call last):
  File "generate_easy.py", line 7, in <module>
    make_package(
  File "pySecDec/make_package.py", line 375, in make_package
    sum_package(
  File "pySecDec/code_writer/sum_package.py", line 480, in sum_package
    template_replacements = [_generate_one_term(
  File "pySecDec/code_writer/sum_package.py", line 480, in <listcomp>
    template_replacements = [_generate_one_term(
  File "pySecDec/code_writer/sum_package.py", line 153, in _generate_one_term
    os.link(filename, filename2)
OSError: [Errno 18] Invalid cross-device link: 'easy_data/easy_integral_coefficient0.txt' -> 'disteval/coefficients/easy_integral_coefficient0.txt'

And indeed, if I manually run

ln easy_data/easy_integral_coefficient0.txt disteval/coefficients/easy_integral_coefficient0.txt

I get:

ln: failed to create hard link 'disteval/coefficients/easy_integral_coefficient0.txt' => 'easy_data/easy_integral_coefficient0.txt': Invalid cross-device link

I guess we can not rely on hard links working on AFS across directories. They do seem to work within the same directory, but not between different ones.