Merge pull request #1526 from rohit-n/build-wx-gtk

Fail CMake if building WX without GTK libraries.

CMakeLists.txt

@@ -685,6 +685,8 @@ if(NOT DISABLE_WX AND NOT ANDROID)
 			include(FindGTK2)
 			if(GTK2_FOUND)
 				include_directories(${GTK2_INCLUDE_DIRS})
+			else()
+				message(FATAL_ERROR "GTK is required to build the WX UI. Please install the GTK development libraries.")
 			endif()
 		endif()
 	endif()