bug#79444: baseenc SIGSEGV on macOS

> > FYI, you probably want to do the following in the CI:
> > 
> >    $ export DEBUG=1
> >    $ export VERBOSE=1
> > 
> > This will save the commands being run and their output. And hopefully
> > make it easier to debug future issues.

Here's the relevant output on macOS 13:

empty1d...
Running command: 'basenc --base64 -d 'empty1d.1' > empty1d.O 2> empty1d.E'
sh: line 1: 79138 Segmentation fault: 11  basenc --base64 -d 'empty1d.1' > empty1d.O 2> empty1d.E
basenc.pl: test empty1d failed: exit status mismatch:  expected 0, got 139
creating file 'empty2d.1' with contents ''
creating file 'empty2d.2' with contents ''
creating file 'empty2d.3' with contents ''
empty2d...
Running command: 'basenc --base64url -d 'empty2d.1' > empty2d.O 2> empty2d.E'
sh: line 1: 79145 Segmentation fault: 11  basenc --base64url -d 'empty2d.1' > empty2d.O 2> empty2d.E
basenc.pl: test empty2d failed: exit status mismatch:  expected 0, got 139
creating file 'empty3d.1' with contents ''
creating file 'empty3d.2' with contents ''
creating file 'empty3d.3' with contents ''
empty3d...
Running command: 'basenc --base32 -d 'empty3d.1' > empty3d.O 2> empty3d.E'
sh: line 1: 79150 Segmentation fault: 11  basenc --base32 -d 'empty3d.1' > empty3d.O 2> empty3d.E
basenc.pl: test empty3d failed: exit status mismatch:  expected 0, got 139
creating file 'empty4d.1' with contents ''
creating file 'empty4d.2' with contents ''
creating file 'empty4d.3' with contents ''
empty4d...
Running command: 'basenc --base32hex -d 'empty4d.1' > empty4d.O 2> empty4d.E'
sh: line 1: 79155 Segmentation fault: 11  basenc --base32hex -d 'empty4d.1' > empty4d.O 2> empty4d.E
basenc.pl: test empty4d failed: exit status mismatch:  expected 0, got 139
creating file 'empty5d.1' with contents ''
creating file 'empty5d.2' with contents ''
creating file 'empty5d.3' with contents ''

and on macOS 15:

empty3d...
Running command: 'basenc --base32 -d 'empty3d.1' > empty3d.O 2> empty3d.E'
sh: line 1: 63973 Segmentation fault: 11  basenc --base32 -d 'empty3d.1' > empty3d.O 2> empty3d.E
basenc.pl: test empty3d failed: exit status mismatch:  expected 0, got 139
creating file 'empty4d.1' with contents ''
creating file 'empty4d.2' with contents ''
creating file 'empty4d.3' with contents ''
empty4d...
Running command: 'basenc --base32hex -d 'empty4d.1' > empty4d.O 2> empty4d.E'
sh: line 1: 63975 Segmentation fault: 11  basenc --base32hex -d 'empty4d.1' > empty4d.O 2> empty4d.E
basenc.pl: test empty4d failed: exit status mismatch:  expected 0, got 139
creating file 'empty5d.1' with contents ''
creating file 'empty5d.2' with contents ''
creating file 'empty5d.3' with contents ''

Bruno