[GTK] Make forwarding headers generation depend on source code
https://bugs.webkit.org/show_bug.cgi?id=137394

Reviewed by Philippe Normand.

Source/WebKit2:

Only run generate-forwarding-headers.pl when source code changes
and use a different target for the symlinks.

* PlatformGTK.cmake:

Tools:

* TestWebKitAPI/CMakeLists.txt: Add missing dependency rule.
* TestWebKitAPI/PlatformGTK.cmake: Only run
generate-forwarding-headers.pl when source code changes.
* WebKitTestRunner/PlatformGTK.cmake: Ditto.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@174422 268f45cc-cd09-0410-ab3c-d52691b4dbfc
Unreviewed, rolling out r174335.
https://bugs.webkit.org/show_bug.cgi?id=137515

It broke EFL layout test totally (Requested by gyuyoung on
#webkit).

Reverted changeset:

"[EFL] Introduce EWebKit_Extension"
https://bugs.webkit.org/show_bug.cgi?id=134921
http://trac.webkit.org/changeset/174335

Patch by Commit Queue <commit-queue@webkit.org> on 2014-10-08

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@174423 268f45cc-cd09-0410-ab3c-d52691b4dbfc