Use a newer version of ffi for Apple M1

[al45tair]

Apple Silicon Macs need a newer version of ffi (I think 1.14 or so).

[onnimonni]

At least on my M1 machine Gem::Platform.local.cpu returns universal instead of arm64 🤷

[jordansissel]

Unfortunately, gem build turns the .gemspec file into YAML which doesn't support executable conditions as your change proposes.

You can observe this by looking at the output, and here's what it looks like when I run it from master:

% gem build fpm.gemspec
% tar -xf fpm-*.gem -O metadata.gz | gzip -dc
...
dependencies:
- !ruby/object:Gem::Dependency
  name: ffi
  requirement: !ruby/object:Gem::Requirement
    requirements:
    - - "~>"
      - !ruby/object:Gem::Version
        version: 1.12.0

I'm still searching for a way to solve this ffi version problem.

[jordansissel]

#1795 -- I'm to try removing ffi from fpm's dependency list.

[jordansissel]

#1785 is resolved by #1786 which removes the ffi dependency entirely from ffi! Woo!

Thank you for this proposed change. I'm closing this now since I believe this issue to be resolved by #1786.

One note, though: I don't have an M1 mac, so I don't have easy access to test that this issue is resolved. If you can, please test the next release and let me know :)