Ruby 3.3+ fix for .gemspec test

Ruby 3.3.0-preview2 causes an '(eval ...' String to be yielded for a
__FILE__ call performed within an `eval`. This String won't work
properly in contexts that expect a String representing a valid
filesystem path.

We don't want to touch the .gemspec file for the sake of the test, and
we don't yet want to refactor out the `eval` call that the test uses, so
for now let's just make sure the test never has to deal with a __FILE__
call within the `eval`.

test/new_relic/gemspec_files_test.rb

@@ -10,9 +10,13 @@ def test_the_test_agent_helper_is_shipped_in_the_gem_files
     skip 'Gemspec test requires a newer version of Rubygems' unless Gem.respond_to?(:open_file)
 
     gem_spec_file_path = File.expand_path('../../../newrelic_rpm.gemspec', __FILE__)
+    gem_spec_content = Gem.open_file(gem_spec_file_path, 'r:UTF-8:-', &:read)
+    # With Ruby 3.3.0-preview2, eval() yields '(eval ...' as the String value
+    # when __FILE__ is used so swap out __FILE__ for the known agent root path
+    gem_spec_content.gsub!('__FILE__', "'#{gem_spec_file_path}'")
 
     Dir.chdir(File.dirname(gem_spec_file_path)) do
-      gem_spec = eval(Gem.open_file(gem_spec_file_path, 'r:UTF-8:-', &:read))
+      gem_spec = eval(gem_spec_content)
 
       assert gem_spec, "Failed to parse '#{gem_spec_file_path}'"
       assert_equal('newrelic_rpm', gem_spec.name)