Exclude pack_extension_job.cc from non windows builds.
Exclude pack_extension_job.cc from non windows builds.

This code relies on extension_creator.cc which is also
currently excluded. This fixes the Linux shared build.

Review URL: http://codereview.chromium.org/175044

git-svn-id: http://src.chromium.org/svn/trunk/src@25155 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 2cacfee452722b7ca8d7589cd4a38be44512882d
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser