fake.rb: set libdir

* tool/fake.rb: set "libdir" to build directory too, so that
  spec/ruby/optional/capi/spec_helper.rb can find libruby_so.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61490 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

tool/fake.rb

@@ -57,6 +57,7 @@ prehook = proc do |extmk|
   mkconfig = RbConfig::MAKEFILE_CONFIG
   mkconfig["builddir"] = config["builddir"] = builddir
   mkconfig["buildlibdir"] = config["buildlibdir"] = builddir
+  mkconfig["libdir"] = config["libdir"] = builddir
   mkconfig["top_srcdir"] = $top_srcdir if $top_srcdir
   mkconfig["extout"] ||= $extout
   config["top_srcdir"] = File.expand_path($top_srcdir ||= top_srcdir)