无法安装指南针

上周我因为bash"易受攻击的问题"而在cygwin上做了更新.
之后我再也无法编译sass了.
我尝试重新安装ruby,在一些安装失败后重新安装cygwin我安装了它并更新了
"gem update --system"
它运行,但当我尝试安装指南针时,我得到以下消息:

> /usr/bin/ruby.exe -r ./siteconf20141006-7856-1td7wzb.rb extconf.rb 
> checking for ffi.h... *** extconf.rb failed ***  Could not create
> Makefile due to some reason, probably lack of necessary  libraries
> and/or headers. Check the mkmf.log file for more details. You may 
> need configuration options.
> 
> Provided configuration options: 
> --with-opt-dir 
> --without-opt-dir 
> --with-opt-include 
> --without-opt-include=${opt-dir}/include 
> --with-opt-lib 
> --without-opt-lib=${opt-dir}/lib 
> --with-make-prog 
> --without-make-prog 
> --srcdir=. 
> --curdir 
> --ruby=/usr/bin/ruby 
> --with-ffi_c-dir 
> --without-ffi_c-dir 
> --with-ffi_c-include 
> --without-ffi_c-include=${ffi_c-dir}/include 
> --with-ffi_c-lib 
> --without-ffi_c-lib=${ffi_c-dir}/ 
> --with-libffi-config 
> --without-libffi-config 
> --with-pkg-config 
> --without-pkg-config  /usr/share/ruby/2.0.0/mkmf.rb:434:in `try_do': The compiler failed to generate an executable file. (RuntimeError) 
> You have to install development tools first.  from
> /usr/share/ruby/2.0.0/mkmf.rb:565:in `try_cpp'  from
> /usr/share/ruby/2.0.0/mkmf.rb:1044:in `block in have_header'  from
> /usr/share/ruby/2.0.0/mkmf.rb:895:in `block in checking_for'  from
> /usr/share/ruby/2.0.0/mkmf.rb:340:in `block (2 levels) in postpone' 
> from /usr/share/ruby/2.0.0/mkmf.rb:310:in `open'  from
> /usr/share/ruby/2.0.0/mkmf.rb:340:in `block in postpone'  from
> /usr/share/ruby/2.0.0/mkmf.rb:310:in `open'  from
> /usr/share/ruby/2.0.0/mkmf.rb:336:in `postpone'  from
> /usr/share/ruby/2.0.0/mkmf.rb:894:in `checking_for'  from
> /usr/share/ruby/2.0.0/mkmf.rb:1043:in `have_header'  from
> extconf.rb:16:in `
'
> 
> extconf failed, exit code 1

我试着安装ffi("gem install ffi"和"gem install ffi --pre"),我得到了同样的消息

这是日志(.gem/ruby​​/extensions/x86_64-cygwin/ffi-1.9.5/gem_make.out)

package configuration for libffi is not found 
"gcc -o conftest.exe -I/usr/include/ruby-2.0.0 -I/usr/include/ruby-2.0.0/ruby/backward -I/usr/include/ruby-2.0.0 -I. -ggdb -O2 -pipe -Wimplicit-function-declaration conftest.c -L. -L/usr/lib -L. -fstack-protector -lruby200 -lpthread -lrt -ldl -lcrypt " 
checked program was: 
/* begin */ 
1: #include "ruby.h" 
2: 
3: int main(int argc, char **argv) 
4: { 
5: return 0; 
6: } 
/* end */

我真的很沮丧!'

系统Windows 7 64位Cygwin