Experiment: add a conditional gemspec

Inspired by:

https://engineering.klarna.com/creating-a-rubygem-compatible-with-ruby-and-jruby-559161bfea2d

Java added to the lockfile with:

    bundle lock --add-platform java

.rubocop.yml

@@ -7,6 +7,7 @@ AllCops:
 Metrics/BlockLength:
   Exclude:
     - "**/*_spec.rb"
+    - "pundit.gemspec"
 
 Metrics/MethodLength:
   Max: 40

Gemfile.lock

@@ -3,6 +3,7 @@ PATH
   specs:
     pundit (2.1.0)
       activesupport (>= 3.0.0)
+      pry
 
 GEM
   remote: https://rubygems.org/
@@ -104,7 +105,6 @@ DEPENDENCIES
   actionpack (>= 3.0.0)
   activemodel (>= 3.0.0)
   bundler
-  pry
   pundit!
   rake
   rspec (>= 3.0.0)
@@ -116,4 +116,4 @@ RUBY VERSION
    ruby 2.6.3p62
 
 BUNDLED WITH
-   2.0.2
+   2.1.4

pundit.gemspec

@@ -23,10 +23,16 @@ Gem::Specification.new do |gem|
   gem.add_development_dependency "actionpack", ">= 3.0.0"
   gem.add_development_dependency "activemodel", ">= 3.0.0"
   gem.add_development_dependency "bundler"
-  gem.add_development_dependency "pry"
   gem.add_development_dependency "rake"
   gem.add_development_dependency "rspec", ">= 3.0.0"
   gem.add_development_dependency "rubocop", "0.74.0"
   gem.add_development_dependency "simplecov", ">= 0.17.0"
   gem.add_development_dependency "yard"
+
+  if RUBY_PLATFORM =~ /java/
+    gem.platform = "java"
+    gem.add_dependency "pry-debugger-jruby"
+  else
+    gem.add_dependency "pry"
+  end
 end