[rubygems/rubygems] Install the best matching gem for the current platform in gem install

Instead of picking essentially a random matching platform

Signed-off-by: Samuel Giddins <segiddins@segiddins.me>

https://github.com/rubygems/rubygems/commit/3727096297

lib/rubygems/resolver.rb

@@ -241,7 +241,7 @@ class Gem::Resolver
 
     sources.each do |source|
       groups[source].
-        sort_by {|spec| [spec.version, spec.platform =~ Gem::Platform.local ? 1 : 0] }. # rubocop:disable Performance/RegexpMatch
+        sort_by {|spec| [spec.version, -Gem::Platform.platform_specificity_match(spec.platform, Gem::Platform.local)] }.
         map {|spec| ActivationRequest.new spec, dependency }.
         each {|activation_request| activation_requests << activation_request }
     end

test/rubygems/test_gem_commands_install_command.rb

@@ -1005,6 +1005,38 @@ ERROR:  Possible alternatives: non_existent_with_hint
     assert_equal %W[a-3-#{local}], @cmd.installed_specs.map(&:full_name)
   end
 
+  def test_install_gem_platform_specificity_match
+    util_set_arch "arm64-darwin-20"
+
+    spec_fetcher do |fetcher|
+      %w[ruby universal-darwin universal-darwin-20 x64-darwin-20 arm64-darwin-20].each do |platform|
+        fetcher.download "a", 3 do |s|
+          s.platform = platform
+        end
+      end
+    end
+
+    @cmd.install_gem "a", ">= 0"
+
+    assert_equal %w[a-3-arm64-darwin-20], @cmd.installed_specs.map(&:full_name)
+  end
+
+  def test_install_gem_platform_specificity_match_reverse_order
+    util_set_arch "arm64-darwin-20"
+
+    spec_fetcher do |fetcher|
+      %w[ruby universal-darwin universal-darwin-20 x64-darwin-20 arm64-darwin-20].reverse_each do |platform|
+        fetcher.download "a", 3 do |s|
+          s.platform = platform
+        end
+      end
+    end
+
+    @cmd.install_gem "a", ">= 0"
+
+    assert_equal %w[a-3-arm64-darwin-20], @cmd.installed_specs.map(&:full_name)
+  end
+
   def test_install_gem_ignore_dependencies_specific_file
     spec = util_spec "a", 2