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: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@25155 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser