add MSVC support for Win32 builds

dev/sfutils/CMakeLists.txt

@@ -1,7 +1,7 @@
 if(APPLE)
   set(CMAKE_C_FLAGS "-O2 -Wall -Dunix -DENABLE_PVX")
 else()
-  if(MINGW)
+  if(MINGW OR MSVC)
     set(CMAKE_C_FLAGS "-O2 -Wall -DENABLE_PVX -DWIN32")
   else()
     set(CMAKE_C_FLAGS "-O2 -Wall -Dlinux -DENABLE_PVX -Dunix")