refactor: add explicit cast in freebsd_pow bit operation (#4960)

Add explicit int32_t cast to clarify the intent of the sign bit
extraction operation, preventing potential signed/unsigned conversion
warnings on stricter compilers while maintaining the portable
implementation.

Author: lum1n0us

core/shared/platform/common/math/math.c

@@ -1408,7 +1408,8 @@ freebsd_pow(double x, double y)
     n = (hx>>31)+1;
        but ANSI C says a right shift of a signed negative quantity is
        implementation defined.  */
-    n = ((u_int32_t)hx >> 31) - 1;
+    /* equal to n = (hx < 0) - 1. But if it works, don't improve it */
+    n = (int32_t)((u_int32_t)hx >> 31) - 1;
 
     /* (x<0)**(non-int) is NaN */
     if ((n | yisint) == 0)