[clang] [OpenCL] Add clang internal extension __cl_clang_non_kernel_scope_local_memory (PR #176726)

[Wenju He via cfe-commits]

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+// RUN: %clang_cc1 %s -triple spir64 -disable-llvm-passes -emit-llvm -o - | FileCheck %s
+
+#pragma OPENCL EXTENSION __cl_clang_non_kernel_scope_local_memory : enable
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wenju-he wrote:

renamed to __cl_clang_local_memory_all_scopes

The restriction in the spec is at https://registry.khronos.org/OpenCL/specs/3.0-unified/html/OpenCL_C.html#_usage_for_declaration_scopes_and_variable_types : `Variables declared in the outermost compound statement inside the body of the kernel function can be qualified by the local or constant address spaces.`

https://github.com/llvm/llvm-project/pull/176726