[CMake] Force 64-bit VS compiler.

Fixes out-of-memory errors in e.g. ProcessLib.

CMakeLists.txt

@@ -9,6 +9,11 @@ cmake_minimum_required(VERSION 3.1)
 cmake_policy(SET CMP0011 NEW)
 cmake_policy(SET CMP0054 NEW)
 
+if(WIN32 AND NOT ${CMAKE_GENERATOR} STREQUAL Ninja)
+    # Force 64-bit VS compiler
+    set(CMAKE_GENERATOR_TOOLSET host=x64)
+endif()
+
 # Project name
 project( OGS-6 )