[EFL][GTK] WebKit2's generate-forwarding-headers.pl runs too many times

[EFL][GTK] WebKit2's generate-forwarding-headers.pl runs too many times
https://bugs.webkit.org/show_bug.cgi?id=142907

Reviewed by Carlos Garcia Campos.

Source/WebKit2:

* PlatformEfl.cmake:
* PlatformGTK.cmake:
* Scripts/generate-forwarding-headers.pl: Make it work with more path and platform arguments.

Tools:

* TestWebKitAPI/PlatformEfl.cmake:
* TestWebKitAPI/PlatformGTK.cmake:
* WebKitTestRunner/PlatformEfl.cmake:
* WebKitTestRunner/PlatformGTK.cmake:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@182595 268f45cc-cd09-0410-ab3c-d52691b4dbfc