Log message:
Update ruby-mini_portile2 to 2.2.0.

### 2.2.0 / 2017-06-04

#### Enhancements

* Remove MD5 hashing of configure options, not avialbale in FIPS mode. (#78)
* Add experimental support for cmake-based projects.
* Retry on HTTP failures during downloads. [#63] (Thanks, @jtarchie and @jvshahid!)
* Support Ruby 2.4 frozen string literals.
* Support applying patches for users with misconfigured git worktree. [#69]
* Support gpg signature verification of download resources.

Log message:
Import ruby-mini_portile2-2.1.0 as misc/ruby-portile2.

Note ruby-mini_portile2 is updated and renamed version of
ruby-mini_portile by the upstream due to backwards-incompatible
behavioral changes from mini_portile 0.7.0.rc* and prior.

This project is a minimalistic implementation of a port/recipe system
for developers.
Because "Works on my machine" is unacceptable for a library maintainer.