Fix const INFINITY issue on MSVC.

We previously hit this for NAN, but it appears the latest version of MSVC used in windows github runners has the same issue for INFINITY.  The same strategy can be applied here.

This will be backported to fix broken release branches.

PiperOrigin-RevId: 700042372

Author: mkruskal-google

upb/message/internal/message.c

@@ -17,9 +17,6 @@
 // Must be last.
 #include "upb/port/def.inc"
 
-const float kUpb_FltInfinity = INFINITY;
-const double kUpb_Infinity = INFINITY;
-
 // The latest win32 SDKs have an invalid definition of NAN.
 // https://developercommunity.visualstudio.com/t/NAN-is-no-longer-compile-time-constant-i/10688907
 //
@@ -30,15 +27,24 @@ const double kUpb_Infinity = INFINITY;
 #if __has_builtin(__builtin_nan)
 #define UPB_NAN __builtin_nan("0")
 #endif
+#if __has_builtin(__builtin_inf)
+#define UPB_INFINITY __builtin_inf()
+#endif
 #endif
 #ifndef UPB_NAN
 #define UPB_NAN 0.0 / 0.0
 #endif
+#ifndef UPB_INFINITY
+#define UPB_INFINITY 1.0 / 0.0
+#endif
 #else
 // For !_WIN32, assume math.h works.
 #define UPB_NAN NAN
+#define UPB_INFINITY INFINITY
 #endif
 
+const float kUpb_FltInfinity = UPB_INFINITY;
+const double kUpb_Infinity = UPB_INFINITY;
 const double kUpb_NaN = UPB_NAN;
 
 bool UPB_PRIVATE(_upb_Message_EnsureAvailable)(struct upb_Message* msg,