Enable multi-processor compilation (microsoft#890)

Author: chris0x44

Release/CMakeLists.txt

@@ -204,6 +204,11 @@ elseif(CMAKE_CXX_COMPILER_ID MATCHES "MSVC")
   set(WARNINGS)
   set(CMAKE_STATIC_LINKER_FLAGS "${CMAKE_STATIC_LINKER_FLAGS} /ignore:4264")
   add_compile_options(/bigobj)
+  set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} /MP")
+  set(CMAKE_CXX_FLAGS_MINSIZEREL "${CMAKE_CXX_FLAGS_MINSIZEREL} /MP")
+  set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} /MP")
+  set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO} /MP")
+  
   if (WINDOWS_STORE OR WINDOWS_PHONE)
     add_compile_options(/ZW)
   endif()