The change in r156811 resulted in several public headers in the JavaScriptCore framework having their modification
date touched on every build, even if their contents had not changed. This resulted in a large portion of WebCore
needing to rebuilt after an incremental build of JavaScriptCore.

Reviewed by Dan Bernstein.

* JavaScriptCore.xcodeproj/project.pbxproj: Have unifdef generate its output to a temporary file. If its exit status
indicates that the content did not change, remove the temporary file. If the content changed, moved the temporary file
over the destination.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@156873 268f45cc-cd09-0410-ab3c-d52691b4dbfc