[CMake][compiler-rt] Use copying instead of symlinking for LSE builtins on non-Unix-likes

[tambre]

Summary

As reported in D93278 post-review symlinking requires privilege escalation on Windows.
Copying is functionally same, so fallback to it for systems that aren't Unix-like.
This is similar to the solution in AddLLVM.cmake.

[tambre]

@ikudrin Thanks for the report on D93278. Could you give this patch a try?

[ikudrin]

The fix resolves the issue on my environment. Thank you for the quick response!

[tambre]

In D98111#2610451, @ikudrin wrote:

The fix resolves the issue on my environment. Thank you for the quick response!

Thanks! I've filed a backport request for 12.0.

compiler-rt/lib/builtins/CMakeLists.txt

set(aarch64_SOURCES
   cpu_model.c
   aarch64/fp_mode.c
 )
 
 # Generate outline atomics helpers from lse.S base
 set(OA_HELPERS_DIR "${CMAKE_CURRENT_BINARY_DIR}/outline_atomic_helpers.dir")
 file(MAKE_DIRECTORY "${OA_HELPERS_DIR}")
 
+if(CMAKE_HOST_UNIX)
+  set(COMPILER_RT_LINK_OR_COPY create_symlink)
+else()
+  set(COMPILER_RT_LINK_OR_COPY copy)
+endif()
+
 foreach(pat cas swp ldadd ldclr ldeor ldset)
   foreach(size 1 2 4 8 16)
     foreach(model 1 2 3 4)
       if(pat STREQUAL "cas" OR NOT size STREQUAL "16")
         set(helper_asm "${OA_HELPERS_DIR}/outline_atomic_${pat}${size}_${model}.S")
         add_custom_command(
           OUTPUT ${helper_asm}
-          COMMAND ${CMAKE_COMMAND} -E create_symlink "${CMAKE_CURRENT_SOURCE_DIR}/aarch64/lse.S" "${helper_asm}"
+          COMMAND ${CMAKE_COMMAND} -E ${COMPILER_RT_LINK_OR_COPY} "${CMAKE_CURRENT_SOURCE_DIR}/aarch64/lse.S" "${helper_asm}"
         )
         set_source_files_properties("${helper_asm}"
           PROPERTIES
           COMPILE_DEFINITIONS "L_${pat};SIZE=${size};MODEL=${model}"
           INCLUDE_DIRECTORIES "${CMAKE_CURRENT_SOURCE_DIR}"
         )
         list(APPEND aarch64_SOURCES "${helper_asm}")
       endif()