[llvm] [SYCL] Add platform enumeration and info query using liboffload (PR #166927)

[Kseniya Tikhomirova via llvm-commits]

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@@ -0,0 +1,8 @@
+#ifndef __SYCL_PARAM_TRAITS_SPEC
+static_assert(false, "__SYCL_PARAM_TRAITS_SPEC is required but not defined");
+#endif
+
+// 4.6.2.4. Information descriptors
+__SYCL_PARAM_TRAITS_SPEC(platform, version, std::string, OL_PLATFORM_INFO_VERSION)
+__SYCL_PARAM_TRAITS_SPEC(platform, name, std::string, OL_PLATFORM_INFO_NAME)
+__SYCL_PARAM_TRAITS_SPEC(platform, vendor, std::string, OL_PLATFORM_INFO_VENDOR_NAME)
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KseniyaTikhomirova wrote:

I am going to apply Andrey's proposal. Please let me know if anyone has objections.
the reason is:
I wanted info descriptors declaration to be independent for SYCL obj in terms of header files (the opposite to what we have in https://github.com/intel/llvm/blob/sycl/sycl/include/sycl/detail/info_desc_helpers.hpp). 
With macro it means pretty low level of unification for helpers. Base class for info desc as proposed by Andrey gives opportunities to achieve the goal I wanted.  Plus 3 people agreed that Offload RT codes should be hidden in SYCL RT that already weakens approach with macros.

I have started implementation of 'device' and there we will be able to check & see how it fits into our code base.

https://github.com/llvm/llvm-project/pull/166927