Build fix for x11_egl target builds

The combination of recent refactor on release branch and merge to
master resulted in a compilation error for the XInitThreads symbol
when using the x11_egl built target.

Components: Framework

VK-GL-CTS Issue: 467

Change-Id: Iba0803e8b73462bd66ab7803a6c90bfd40d9164c
diff --git a/framework/platform/lnx/tcuLnxPlatform.cpp b/framework/platform/lnx/tcuLnxPlatform.cpp
index 1b27702..0c7bc94 100644
--- a/framework/platform/lnx/tcuLnxPlatform.cpp
+++ b/framework/platform/lnx/tcuLnxPlatform.cpp
@@ -30,6 +30,10 @@
 #include "gluPlatform.hpp"
 #include "vkPlatform.hpp"
 
+#if defined (DEQP_SUPPORT_X11)
+#	include <X11/Xlib.h>
+#endif // DEQP_SUPPORT_X11
+
 #if defined (DEQP_SUPPORT_GLX)
 #	include "tcuLnxX11GlxPlatform.hpp"
 #endif // DEQP_SUPPORT_GLX