这个是我在SO上的提问，可以去看一下。

过程：

sudo gem install eventmachine

...

Building native extensions.  This could take a while...
/Users/kuankuan/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/rubygems/ext/builder.rb:48: warning: Insecure world writable dir /usr/local/bin/g4bin in PATH, mode 040777
ERROR:  Error installing eventmachine:
    ERROR: Failed to build gem native extension.

        /Users/kuankuan/.rvm/rubies/ruby-1.9.3-p327/bin/ruby extconf.rb
/Users/kuankuan/.rvm/rubies/ruby-1.9.3-p327/lib/ruby/1.9.1/mkmf.rb:1344: warning: Insecure world writable dir /usr/local/bin/g4bin in PATH, mode 040777
checking for rb_trap_immediate in ruby.h,rubysig.h... no
checking for rb_thread_blocking_region()... yes
checking for inotify_init() in sys/inotify.h... no
checking for __NR_inotify_init in sys/syscall.h... no
checking for writev() in sys/uio.h... yes
checking for rb_thread_check_ints()... yes
checking for rb_time_new()... yes
checking for sys/event.h... yes
checking for sys/queue.h... yes
creating Makefile

make
compiling binder.cpp
cc1plus: error: unrecognized command line option "-arch"
make: *** [binder.o] Error 1

ruby版本：1.9.3 Mac OSX 10.8.3