Allow installing RDoc from a git source

Co-authored-by: Stan Lo <st0012@users.noreply.github.com>

Author: vinistock

ext/rdoc/extconf.rb

@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+# Generate all parse files using racc and kpeg. This is not necessary for regular gem installation, but it is when
+# installing RDoc from the git source. Without this, the generated parse files would not exist and RDoc would not work
+system("gem install kpeg && rake generate") if Dir.exist?(File.join("..", "..", ".git"))
+
+# RDoc doesn't actually have a native extension, but a Makefile needs to exist in order to successfully install the gem
+require "mkmf"
+create_makefile("rdoc/rdoc")

rdoc.gemspec

@@ -35,6 +35,7 @@ RDoc includes the +rdoc+ and +ri+ tools for generating and displaying documentat
   s.bindir = "exe"
   s.executables = ["rdoc", "ri"]
   s.require_paths = ["lib"]
+  s.extensions = ["ext/rdoc/extconf.rb"]
   # for ruby core repository. It was generated by
   # `git ls-files -z`.split("\x0").each {|f| puts "    #{f.dump}," unless f.start_with?(*%W[test/ spec/ features/ .]) }
   s.files = [