Avoid keeping the preinitialized home path in the image heap

* Also reduces the amount of code to run during patchContext().

Author: eregon

src/main/ruby/truffleruby/post-boot/post-boot.rb

@@ -71,14 +71,21 @@
   if old_home
     # We need to fix all paths which capture the image build-time home to point
     # to the runtime home.
+
+    paths_starting_with_home = []
+    [$LOAD_PATH, $LOADED_FEATURES].each do |array|
+      array.each do |path|
+        if path.start_with?(old_home)
+          paths_starting_with_home << path[old_home.size..-1]
+        end
+      end
+    end
+    old_home = nil
+
     Truffle::Boot.delay do
       new_home = Truffle::Boot.ruby_home
-      [$LOAD_PATH, $LOADED_FEATURES].each do |array|
-        array.each do |path|
-          if path.start_with?(old_home)
-            path.replace(new_home + path[old_home.size..-1])
-          end
-        end
+      paths_starting_with_home.each do |path|
+        path.replace(new_home + path)
       end
     end
   end