error about installing json

bundle install --binstubsをすると

Installing json (1.7.5) 
Errno::EPERM: Operation not permitted - /Users/nakazatomasaya/.rvm/gems/ruby-1.9.3-p194/gems/json-1.7.5/.gitignore
An error occurred while installing json (1.7.5), and Bundler cannot continue.
Make sure that `gem install json -v '1.7.5'` succeeds before bundling.

jsonの部分でエラーが出る。なので
gem install json -v '1.7.5'をすると

ERROR:  While executing gem ... (Errno::EPERM)
Operation not permitted - /Users/nakazatomasaya/.rvm/gems/ruby-1.9.3-p194/gems/json-1.7.5/.gitignore

sudo gem install json -v '1.7.5'でやると


Building native extensions.  This could take a while...
ERROR:  Error installing json:
	ERROR: Failed to build gem native extension.

        /Users/nakazatomasaya/.rvm/rubies/ruby-1.9.3-p194/bin/ruby extconf.rb
creating Makefile

make
compiling generator.c
make: /usr/bin/gcc-4.2: No such file or directory
make: *** [generator.o] Error 1


Gem files will remain installed in /Users/nakazatomasaya/.rvm/gems/ruby-1.9.3-p194/gems/json-1.7.5 for inspection.
Results logged to /Users/nakazatomasaya/.rvm/gems/ruby-1.9.3-p194/gems/json-1.7.5/ext/json/ext/generator/gem_make.out