calabash-android ERROR: Failed to build gem native extension.

>gem install calabash-android
Fetching: builder-3.2.2.gem (100%)
Fetching: diff-lcs-1.2.5.gem (100%)
Fetching: multi_json-1.11.2.gem (100%)
Fetching: gherkin-2.12.2-x86-mingw32.gem (100%)
Fetching: multi_test-0.1.2.gem (100%)
Fetching: cucumber-1.3.20.gem (100%)
Fetching: json-1.8.3.gem (100%)
Building native extensions.  This could take a while...
ERROR:  Error installing calabash-android:
        ERROR: Failed to build gem native extension.

        D:/ruby/Ruby193/bin/ruby.exe extconf.rb
creating Makefile

make
generating generator-i386-mingw32.def
compiling generator.c
In file included from generator.c:1:0:
../fbuffer/fbuffer.h:5:18: fatal error: ruby.h: No such file or directory
compilation terminated.
make: *** [generator.o] Error 1


Gem files will remain installed in D:/ruby/Ruby193/lib/ruby/gems/1.9.1/gems/json-1.8.3 for inspection.
Results logged to D:/ruby/Ruby193/lib/ruby/gems/1.9.1/gems/json-1.8.3/ext/json/ext/generator/gem_make.out

gemをupdateしてみた。ダメだった。変化なし。

gem update

Rubyを2.2へアップし、DevKitを入れたところ、動くようになった。

Error installing calabash-android on Windows