[GTK] Read fonts path when running layout tests from alternative fonts dir when main...

[GTK] Read fonts path when running layout tests from alternative fonts dir when main dir doesn't exist
https://bugs.webkit.org/show_bug.cgi?id=89437

Reviewed by Martin Robinson.

If main fonts directory doesn't exist, try with an alternative
fonts directory at build directory.

* DumpRenderTree/gtk/DumpRenderTree.cpp:
(getOutputDir):
(getFontsPath):
(initializeFonts):
* WebKitTestRunner/InjectedBundle/gtk/ActivateFontsGtk.cpp:
(WTR::getOutputDir):
(WTR):
(WTR::getFontsPath):
(WTR::inititializeFontConfigSetting):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@121684 268f45cc-cd09-0410-ab3c-d52691b4dbfc