Introduce --basedir to insns2vm.rb

and leverage that to preserve the directory structure under tool/ruby_vm/views

tool/ruby_vm/controllers/application_controller.rb

@@ -16,10 +16,11 @@ require_relative '../models/typemap'
 require_relative '../loaders/vm_opts_h'
 
 class ApplicationController
-  def generate i, destdir
+  def generate i, destdir, basedir
     path = Pathname.new i
     dst = destdir ? Pathname.new(destdir).join(i) : Pathname.new(i)
-    dumper = RubyVM::Dumper.new dst
+    base = basedir ? Pathname.new(basedir) : Pathname.pwd
+    dumper = RubyVM::Dumper.new dst, base.expand_path
     return [path, dumper]
   end
 end