Add script to setup codesigning on macOS

[Joel Brobecker]

> I’m interested in setting up a macOS build of GDB on conda-forge ([1],
> [2]) and it seems that in order to do it the codesigning procedure
> would have to be automated, i.e. entirely command-line driven.  The
> LLDB project already has a script doing exactly that [3], and I was
> thinking of adding such a script to the conda-forge GDB feedstock.
> However, I thought it could be a good idea to add it directly to the
> GDB repository. Would a patch adding such a script be well received  ?

Not speaking for the entire group, but from my perspective,
I don't see an objection off-hand to the idea of having it in
the GDB repository. However, the GDB projects only accepts
contributions that are either small or obvious enough to be
accepted as is. For other contributions such as this one (IMO)
that do not qualify, you need to be able to assign the copyrigh
of that file to the FSF (need copyright assignment on file, and
have permission to assign the copyright to the FSF).

-- 
Joel