gem install rails fails at binding_of_caller gem

Question

I'm trying to get rails working and can't get past a binding_of_caller gem that tries to install with the other gems after running sudo gem install rails. I don't think the gem is required for rails to work, but can't figure out how to skip it, or stop it from trying to install.

Every time the list of gems gets to binding_of_callers I get the following:

Installing binding_of_callers (0.6.9) with native extensions

Gem::Installer::ExtensionBuildError: 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. -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE   -fno-common -arch i386 -arch x86_64 -g -Os -pipe -fno-common -DENABLE_DTRACE  -fno-common  -pipe -fno-common  -O0 -std=c99  -c binding_of_caller.c
binding_of_caller.c:4:10: fatal error: 'vm_core.h' file not found
#include "vm_core.h"
         ^
1 error generated.
make: *** [binding_of_caller.o] Error 1


Gem files will remain installed in /Users/ericavirtue/.bundler/tmp/54559/gems/binding_of_caller-0.6.9 for inspection.
Results logged to /Users/ericavirtue/.bundler/tmp/54559/gems/binding_of_caller-0.6.9/ext/binding_of_caller/gem_make.out
An error occurred while installing binding_of_caller (0.6.9), and Bundler cannot continue.
Make sure that `gem install binding_of_caller -v '0.6.9'` succeeds before bundling.

I'm running OSX 10.8.2 and using pow web server with rbenv to manage ruby. I'm also running ruby 1.9.3-p385

Answer 1

Try updating the gem:

$ bundle update binding_of_caller

Answer 2

Before installing Rails, add the gem with the following (also note that the gem name is singular):

$ gem install binding_of_caller

Then run:

$ bundle update rails

Or:

$ gem install rails

(Or whatever rbenv offers)