问therubyracer安装错误

EN

~/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1> gem install libv8
Building native extensions.  This could take a while...
Successfully installed libv8-3.11.8.3
1 gem installed
Installing ri documentation for libv8-3.11.8.3...
Installing RDoc documentation for libv8-3.11.8.3...

~/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1> gem install therubyracer
Building native extensions.  This could take a while...
ERROR:  Error installing therubyracer:
    ERROR: Failed to build gem native extension.

        /Users/rdp/.rvm/rubies/ruby-1.9.3-p125/bin/ruby extconf.rb
checking for main() in -lobjc... *** 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
    --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/rdp/.rvm/rubies/ruby-1.9.3-p125/bin/ruby
    --with-objclib
    --without-objclib
/Users/rdp/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:381:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.
    from /Users/rdp/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:461:in `try_link0'
    from /Users/rdp/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:476:in `try_link'
    from /Users/rdp/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:619:in `try_func'
    from /Users/rdp/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:845:in `block in have_library'
    from /Users/rdp/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:790:in `block in checking_for'
    from /Users/rdp/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:284:in `block (2 levels) in postpone'
    from /Users/rdp/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:254:in `open'
    from /Users/rdp/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:284:in `block in postpone'
    from /Users/rdp/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:254:in `open'
    from /Users/rdp/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:280:in `postpone'
    from /Users/rdp/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:789:in `checking_for'
    from /Users/rdp/.rvm/rubies/ruby-1.9.3-p125/lib/ruby/1.9.1/mkmf.rb:840:in `have_library'
    from extconf.rb:10:in `<main>'


Gem files will remain installed in /Users/rdp/.rvm/gems/ruby-1.9.3-p125/gems/therubyracer-0.10.1 for inspection.
Results logged to /Users/rdp/.rvm/gems/ruby-1.9.3-p125/gems/therubyracer-0.10.1/ext/v8/gem_make.out

"/usr/bin/gcc-4.2 -o conftest -I/Users/rdp/.rvm/rubies/ruby-1.9.3-p125/include/ruby-1.9.1/x86_64-darwin11.3.0 -I/Users/rdp/.rvm/rubies/ruby-1.9.3-p125/include/ruby-1.9.1/rub\
y/backward -I/Users/rdp/.rvm/rubies/ruby-1.9.3-p125/include/ruby-1.9.1 -I. -I/Users/rdp/.rvm/usr/include -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE    -O3 -ggdb -Wextra -Wno-unused-\
parameter -Wno-parentheses -Wno-long-long -Wno-missing-field-initializers -Wpointer-arith -Wwrite-strings -Wdeclaration-after-statement -Wshorten-64-to-32 -Wimplicit-functio\
n-declaration  -fno-common -pipe conftest.c  -L. -L/Users/rdp/.rvm/rubies/ruby-1.9.3-p125/lib -L/Users/rdp/.rvm/usr/lib -L.      -lruby.1.9.1  -lpthread -ldl -lobjc "
checked program was:
/* begin */
1: #include "ruby.h"
2:
3: int main() {return 0;}
/* end */