/Users/oalo/.rvm/rubies/ruby-1.9.2-p180/bin/ruby extconf.rb
checking for sysctl()... *** 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=/Users/oalo/.rvm/rubies/ruby-1.9.2-p180/bin/ruby
/Users/oalo/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/mkmf.rb:368:in `try_do': The complier failed to generate an executable file. (RuntimeError)
You have to install development tools first.
    from /Users/oalo/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/mkmf.rb:435:in `try_link0'
    from /Users/oalo/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/mkmf.rb:440:in `try_link'
    from /Users/oalo/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/mkmf.rb:552:in `try_func'
    from /Users/oalo/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/mkmf.rb:797:in `block in have_func'
    from /Users/oalo/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/mkmf.rb:693:in `block in checking_for'
    from /Users/oalo/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/mkmf.rb:280:in `block (2 levels) in postpone'
    from /Users/oalo/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/mkmf.rb:254:in `open'
    from /Users/oalo/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/mkmf.rb:280:in `block in postpone'
    from /Users/oalo/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/mkmf.rb:254:in `open'
    from /Users/oalo/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/mkmf.rb:276:in `postpone'
    from /Users/oalo/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/mkmf.rb:692:in `checking_for'
    from /Users/oalo/.rvm/rubies/ruby-1.9.2-p180/lib/ruby/1.9.1/mkmf.rb:796:in `have_func'
    from extconf.rb:5:in `<main>'