Use the correct macro check if we are compiling for windows

src/ftxui/screen/screen.cpp

@@ -7,7 +7,8 @@
 #include "ftxui/screen/string.hpp"
 #include "ftxui/screen/terminal.hpp"
 
-#if defined(WIN32)
+
+#if defined(_WIN32)
   #define WIN32_LEAN_AND_MEAN
   #define NOMINMAX
   #include <Windows.h>
@@ -75,7 +76,7 @@ Screen::Screen(int dimx, int dimy)
       dimx_(dimx),
       dimy_(dimy),
       pixels_(dimy, std::vector<Pixel>(dimx)) {
-#if defined(WIN32)
+#if defined(_WIN32)
   // The placement of this call is a bit weird, however we can assume that
   // anybody who instantiates a Screen object eventually wants to output
   // something to the console.

src/ftxui/screen/terminal.cpp

@@ -2,7 +2,8 @@
 
 #include <stdio.h>
 
-#if defined(WIN32)
+
+#if defined(_WIN32)
   #define WIN32_LEAN_AND_MEAN
   #define NOMINMAX
   #include <Windows.h>
@@ -18,7 +19,7 @@ namespace ftxui {
 Terminal::Dimensions Terminal::Size() {
 #if defined(__EMSCRIPTEN__)
   return Dimensions{80, 43};
-#elif defined(WIN32)
+#elif defined(_WIN32)
   CONSOLE_SCREEN_BUFFER_INFO csbi;
   int columns, rows;