title: Failed to build json (1.6.3) with native extension after I installed Xcode 4.2
body: <p>Are you familiar with this error? I have no idea how to fix this:</p>
  
  <pre><code>Installing json (1.6.3) with native extensions  Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.
  
          /Users/boris/.rvm/rubies/ruby-1.9.2-p290/bin/ruby extconf.rb  creating Makefile
  
  make /usr/bin/gcc-4.2 -I.
  -I/Users/boris/.rvm/rubies/ruby-1.9.2-p290/include/ruby-1.9.1/x86_64-darwin10.8.0
  -I/Users/boris/.rvm/rubies/ruby-1.9.2-p290/include/ruby-1.9.1/ruby/backward
  -I/Users/boris/.rvm/rubies/ruby-1.9.2-p290/include/ruby-1.9.1 -I. -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE   -fno-common -O3 -ggdb -Wextra -Wno-unused-parameter -Wno-parentheses -Wpointer-arith -Wwrite-strings -Wno-missing-field-initializers -Wshorten-64-to-32 -Wno-long-long  -fno-common -pipe -O3 -Wall  -o parser.o -c parser.c make: /usr/bin/gcc-4.2: No such file or directory make: *** [parser.o] Error 1
  
  
  Gem files will remain installed in /Users/boris/.rvm/gems/ruby-1.9.2-p290@apps2/gems/json-1.6.3 for inspection. Results logged to /Users/boris/.rvm/gems/ruby-1.9.2-p290@apps2/gems/json-1.6.3/ext/json/ext/parser/gem_make.out An error occured while installing json (1.6.3), and Bundler cannot continue. Make sure that `gem install json -v '1.6.3'` succeeds before bundling.
  </code></pre>
  
  <p>System info:</p>
  
  <pre><code>gem -v
  1.8.10
  $ ruby -v
  ruby 1.9.2p290 (2011-07-09 revision 32553) [x86_64-darwin10.8.0]
  </code></pre>
  
  <p>Xcode v4.2.1</p>