[llvm] [SYCL] Add libsycl, a SYCL RT library implementation project (PR #144372)

[Kseniya Tikhomirova via llvm-commits]

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@@ -0,0 +1,128 @@
+#===============================================================================
+# Setup Project
+#===============================================================================
+cmake_minimum_required(VERSION 3.20.0)
+
+set(LLVM_SUBPROJECT_TITLE "libsycl")
+
+set(LIBSYCL_SOURCE_DIR  ${CMAKE_CURRENT_SOURCE_DIR})
+set(LIBSYCL_BINARY_DIR  ${CMAKE_CURRENT_BINARY_DIR})
+
+set(CMAKE_CXX_STANDARD 17 CACHE STRING "C++ standard to conform to")
+set(CMAKE_CXX_STANDARD_REQUIRED YES)
+set(CMAKE_CXX_EXTENSIONS OFF)
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KseniyaTikhomirova wrote:

IMHO "The original code is consistent with what is done for many projects." is not correct. 
Other projects has 2 build "options":
- STANDALONE build (where value is cached, "the original code" : https://github.com/llvm/llvm-project/blob/main/openmp/CMakeLists.txt#L23)
- not STANDALONE (where value is **not** cached: https://github.com/llvm/llvm-project/blob/main/openmp/CMakeLists.txt#L86): 

We have not provided any standalone build options yet so I think current code is aligned with other RTs.


https://github.com/llvm/llvm-project/pull/144372