Ruby/Other: Fix for missing header files on Mac OSX 10.6

Having trouble installing certain Ruby gems (mysql) on Mac OSX 10.6?   MacPorts ?

Error message similar to this?:

mkmf.rb can’t find header files for ruby at /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/ruby.h

Solution: Reinstall Xcode.   To verify this problem,  you can run ‘which make’ from terminal and most likely you will receive no response if you are getting the missing header file error.