That's probably a bug in the gsl-devel port and you should file it as such. The Portfile tries to call install-info
on a file that might not even be available anymore at the point of the installation process at which it is being called.
Since MacPorts 2.2, MacPorts uses sandboxing to prevent build systems (and commands called from Portfiles) from touching files outside the locations where they should – that's probably why you see the Operation not permitted
error.
Instead of the gsl-devel
port, just install the gsl
port. It provides the same files and is also newer.