[SYCL][Unittests] Check for C++20 support before enabling IPC tests (#20874)

This commit changes the CMake for the IPC unittests to check for C++20
support before enabling the tests.

Signed-off-by: Larsen, Steffen <steffen.larsen@intel.com>

Author: steffenlarsen

sycl/unittests/Extensions/InterProcessCommunication/CMakeLists.txt

@@ -1,6 +1,8 @@
-add_sycl_unittest(IPCTests OBJECT
-  Memory.cpp
-)
+if("cxx_std_20" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
+  add_sycl_unittest(IPCTests OBJECT
+    Memory.cpp
+  )
 
-set_target_properties(IPCTests_Preview_Tests PROPERTIES CXX_STANDARD 20)
-set_target_properties(IPCTests_Non_Preview_Tests PROPERTIES CXX_STANDARD 20)
+  target_compile_features(IPCTests_Preview_Tests PUBLIC cxx_std_20)
+  target_compile_features(IPCTests_Non_Preview_Tests PUBLIC cxx_std_20)
+endif()