devel/ruby-pkg-config: update to 1.5.1

1.5.0 (2022-11-23)

Improvements

* Improved the default search path.  "pkg-config --variable=pc_path
  pkg-config" is used as the default search path if it's available.
  [Reported by Watson][GitHub:#22]

1.5.1 (2022-11-23)

Improvements

* Improved the default search path. "/usr" in "/usr/bin/pkg-config" isn't
  used for buidling the default search path if "pkg-config
  --variable=pc_path pkg-config" is available.  [Reported by
  Watson][GitHub:#22]

(taca)