ruby says this:

$ ruby setup.rb all
Processing the package `cairo' ...
---> lib
<--- lib
---> ext
/usr/local/bin/ruby /home/Administrator/rcairo-1.2.0/packages/cairo/ext/extconf.rb
checking for GCC... yes
checking for cairo version (>= 1.2.0)... no
*** /home/Administrator/rcairo-1.2.0/packages/cairo/ext/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=/home/Administrator/rcairo-1.2.0/packages/cairo/ext
        --curdir
        --ruby=/usr/local/bin/ruby
        --with-pkg-config
        --without-pkg-config
setup.rb:656:in `command': system("/usr/local/bin/ruby" "/home/Administrator/rcairo-1.2.0/packages/c
airo/ext/extconf.rb") failed (RuntimeError)
        from setup.rb:661:in `ruby'
        from setup.rb:1237:in `extconf'
        from setup.rb:1233:in `config_dir_ext'
        from setup.rb:1498:in `traverse'
        from setup.rb:1515:in `dive_into'
        from setup.rb:1496:in `traverse'
        from setup.rb:1490:in `exec_task_traverse'
        from setup.rb:1485:in `exec_task_traverse'
        from setup.rb:1220:in `exec_config'



mkmf.log says this:

"gcc -c -I. -I/usr/local/lib/ruby/1.8/i386-cygwin  -g -O2    conftest.c"
checked program was:
/* begin */
/*top*/
#ifndef __GNUC__
# error
>>>>>> __GNUC__ undefined <<<<<<
#endif
/* end */