doc: Exclude build system sources from RDoc

Author: kateinoigakukun

tasks/doc.rake

@@ -4,5 +4,5 @@ require "ruby_wasm/version"
 RDoc::Task.new do |doc|
   doc.main = "README.md"
   doc.title = "ruby.wasm #{RubyWasm::VERSION} Documentation"
-  doc.rdoc_files = FileList.new %w[*.md lib/**/*.rb ext/**/*.c ext/**/*.rb]
+  doc.rdoc_files = FileList.new %w[*.md ext/**/*.c ext/**/*.rb]
 end