Fix Cycles build in VS2022, use explicit two's complement in find_first_set()

Compiling Cycles in Visual Studio 2022 yields the error:
C4146: unary minus operator applied to unsigned type, result still unsigned

Replacing it with explicit two's complement achieves the same result as signed
negation but avoids the error.

Differential Revision: https://developer.blender.org/D16616

intern/cycles/util/math.h

@@ -860,7 +860,7 @@ ccl_device_inline uint find_first_set(uint x)
   return (x != 0) ? ctz(x) + 1 : 0;
 #else
 #  ifdef _MSC_VER
-  return (x != 0) ? (32 - count_leading_zeros(x & (-x))) : 0;
+  return (x != 0) ? (32 - count_leading_zeros(x & (~x + 1))) : 0;
 #  else
   return __builtin_ffs(x);
 #  endif