Bring back LDFLAGS workaround for Ruby 2.1.1

People are reporting that they are still getting errors:

  something wrong with LDFLAGS="-L/Users/<user>/.rbenv/versions/2.1.1/lib "

It was removed in 97b9999 because we
thought Ruby build process doesn't need it anymore. Turns out it does,
and this workaround is effective for the rest of Ruby 2.1.x anyway.

share/ruby-build/2.1.1

@@ -1,3 +1,3 @@
 install_package "yaml-0.1.6" "http://pyyaml.org/download/libyaml/yaml-0.1.6.tar.gz#7da6971b4bd08a986dd2a61353bc422362bd0edcc67d7ebaac68c95f74182749" --if needs_yaml
 install_package "openssl-1.0.1p" "https://www.openssl.org/source/openssl-1.0.1p.tar.gz#bd5ee6803165c0fb60bbecbacacf244f1f90d2aa0d71353af610c29121e9b2f1" mac_openssl --if has_broken_mac_openssl
-install_package "ruby-2.1.1" "https://cache.ruby-lang.org/pub/ruby/2.1/ruby-2.1.1.tar.gz#c843df31ae88ed49f5393142b02b9a9f5a6557453805fd489a76fbafeae88941" standard verify_openssl
+install_package "ruby-2.1.1" "https://cache.ruby-lang.org/pub/ruby/2.1/ruby-2.1.1.tar.gz#c843df31ae88ed49f5393142b02b9a9f5a6557453805fd489a76fbafeae88941" ldflags_dirs standard verify_openssl