The script for flex and bison was not being generated properly on linux. Extra quotes were being generated in the command-line around output-file path. This change gets around the problem by expanding string variables instead of list. This has another nice side effect that output file path need not be repeated twice.
Review URL: http://codereview.appspot.com/1163041

git-svn-id: https://angleproject.googlecode.com/svn/trunk@253 736b8ea6-26fd-11df-bfd4-992fa37f6226