Package all files in packaged .gem

Author: kateinoigakukun

lib/ruby_wasm/packager/file_system.rb

@@ -115,7 +115,14 @@ def each_gem_content_path(&block)
     @packager.specs.each do |spec|
       next unless File.exist?(spec.full_gem_path)
 
-      spec.files
+      # spec.files is only valid before the gem is packaged.
+      if spec.source.path?
+        relative_paths = spec.files
+      else
+        # All files in .gem are required.
+        relative_paths = Dir.children(spec.full_gem_path)
+      end
+      relative_paths
         .each do |require_path|
           source = File.expand_path(require_path, spec.full_gem_path)
           next unless File.exist?(source)