diff -u -r ../ruby-2.2.1/tool/rbinstall.rb ./tool/rbinstall.rb
--- ../ruby-2.2.1/tool/rbinstall.rb	2014-12-26 01:44:52.000000000 -0500
+++ ./tool/rbinstall.rb	2015-03-06 15:12:16.276142782 -0500
@@ -656,7 +656,7 @@
 install?(:ext, :comm, :gem) do
   $:.unshift(File.join(srcdir, "lib"))
   require("rubygems.rb")
-  gem_dir = Gem.default_dir
+  gem_dir = '@TERMUX_PREFIX@/var/lib/gems/2.2.0'
   directories = Gem.ensure_gem_subdirectories(gem_dir, :mode => $dir_mode)
   prepare "default gems", gem_dir, directories
 
@@ -715,7 +715,7 @@
   end
   if defined?(Zlib)
     require 'pathname'
-    gem_dir = Gem.default_dir
+    gem_dir = '@TERMUX_PREFIX@/var/lib/gems/2.2.0'
     directories = Gem.ensure_gem_subdirectories(gem_dir, :mode => $dir_mode)
     prepare "bundle gems", gem_dir, directories
     Dir.glob(srcdir+'/gems/*.gem').each do |gem|