Rename TARGET_OS_* to HOST_OS_*.

runtime/platform/floating_point_win.cc

Index: runtime/platform/floating_point_win.cc
diff --git a/runtime/platform/floating_point_win.cc b/runtime/platform/floating_point_win.cc
index 8863ec5f8f090630f2eb463b8b31839f3d58a6d9..7fffe7aa2cc363d67e5a73a65a2a35ed9897be37 100644
--- a/runtime/platform/floating_point_win.cc
+++ b/runtime/platform/floating_point_win.cc
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
-#if defined(TARGET_OS_WINDOWS)
+#if defined(HOST_OS_WINDOWS)
 
 #include "platform/floating_point_win.h"
 
@@ -46,4 +46,4 @@ double atan2_ieee(double x, double y) {
   }
 }
 
-#endif  // defined(TARGET_OS_WINDOWS)
+#endif  // defined(HOST_OS_WINDOWS)