[orc-rt] Replace size_t with std::size_t in Math.h. (Fixes unit test on Linux)

Author: lhames

orc-rt/include/orc-rt/Math.h

@@ -25,7 +25,7 @@ template <typename T> constexpr bool isPowerOf2(T Val) noexcept {
 
 /// Calculates the next power of 2.
 template <typename T> constexpr T nextPowerOf2(T Val) noexcept {
-  for (size_t I = 1; I < std::numeric_limits<T>::digits; I <<= 1)
+  for (std::size_t I = 1; I < std::numeric_limits<T>::digits; I <<= 1)
     Val |= (Val >> I);
   return Val + 1;
 }