Ruby on rails 安装gem'时出错；scrapi'；

我已经使用rubyinstaller安装了Ruby1.9.3

我执行：

gem安装scrapi

我得到以下信息：

Gem files will remain installed in C:/Ruby193/lib/ruby/gems/1.9.1/gems/ffi-1.0.1
1 for inspection.
Results logged to C:/Ruby193/lib/ruby/gems/1.9.1/gems/ffi-1.0.11/ext/ffi_c/gem_m
ake.out

gem_make.out

文件包含以下信息：

C:/Ruby193/bin/ruby.exe extconf.rb
checking for ffi.h... no
checking for ffi.h in /usr/local/include... no
checking for rb_thread_blocking_region()... yes
checking for ruby_native_thread_p()... yes
checking for rb_thread_call_with_gvl()... yes
creating extconf.h
creating Makefile

make
libffi.gnu.mk:24: *** target pattern contains no `%'.  Stop.

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有什么想法吗？

安装DevKit解决了这个问题：