Failed to install cocoapods with 'sudo gem install cocoapods'

Failed to install cocoapods with 'sudo gem install cocoapods'

Mac OS 10.8.4, Xcode 4.6.3, Command Line Tools installed.
At last, I got this:
Building native extensions. This could take a while...
ERROR: Error installing cocoapods:
ERROR: Failed to build gem native extension.
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby
extconf.rb
creating Makefile
make
xcrun cc -I.
-I/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/universal-darwin12.0
-I/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/universal-darwin12.0
-I. -DJSON_GENERATOR -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -fno-common
-arch i386 -arch x86_64 -g -O3 -pipe -fno-common -DENABLE_DTRACE
-fno-common -pipe -fno-common -c generator.c
clang: error: unable to execute command: posix_spawn failed: No such file
or directory
clang: error: lipo command failed due to signal (use -v to see invocation)
Apple LLVM version 4.2 (clang-425.0.28) (based on LLVM 3.2svn)
Target: x86_64-apple-darwin12.4.0
Thread model: posix
clang: note: diagnostic msg: PLEASE submit a bug report to
http://developer.apple.com/bugreporter/ and include the crash backtrace,
preprocessed source, and associated run script.
clang: note: diagnostic msg: Error generating preprocessed source(s) -
cannot generate preprocessed source with multiple -arch options.
make: *** [generator.o] Error 255
Gem files will remain installed in /Library/Ruby/Gems/1.8/gems/json-1.8.0
for inspection.
Results logged to
/Library/Ruby/Gems/1.8/gems/json-1.8.0/ext/json/ext/generator/gem_make.out