Align size of spec_constant class between host and device

Added a padding field to device representation of spec_constant class in
order to align its size with size of it on host. If sizes are not the
same it could lead to memory corruptions in SYCL RT when it tries to
access arguments of SYCL Kernel function.

Author: AlexeySachkov

sycl/CMakeLists.txt

@@ -39,6 +39,8 @@ if(SYCL_ENABLE_WERROR)
   endif()
 endif()
 
+add_definitions(-g)
+
 # Create a soft option for enabling or disabling the instrumentation
 # of the SYCL runtime and expect enabling
 option(SYCL_ENABLE_XPTI_TRACING "Enable tracing of SYCL constructs" OFF)

sycl/include/CL/sycl/ONEAPI/experimental/spec_constant.hpp

@@ -42,7 +42,9 @@ template <typename T, typename ID = T> class spec_constant {
   spec_constant(T Cst) : Val(Cst) {}
 
   T Val;
-#endif
+#else
+  char padding[sizeof(T)];
+#endif // __SYCL_DEVICE_ONLY__
   friend class cl::sycl::program;
 
 public: