[llvm] [CMake] Support per-target linker flags (PR #68393)

[Petr Hosek via llvm-commits]

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@@ -1524,6 +1528,13 @@ macro(add_llvm_tool_subdirectory name)
   add_llvm_external_project(${name})
 endmacro(add_llvm_tool_subdirectory)
 
+macro(add_custom_linker_flags name)
+  if (LLVM_${name}_LINKER_FLAGS)
+    message(STATUS "Applying ${LLVM_${name}_LINKER_FLAGS} to ${name}")
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petrhosek wrote:

An alternative to an option would be to use the `DEBUG` mode instead of `STATUS` so developers can use [`CMAKE_MESSAGE_LOG_LEVEL`](https://cmake.org/cmake/help/latest/variable/CMAKE_MESSAGE_LOG_LEVEL.html#variable:CMAKE_MESSAGE_LOG_LEVEL) to suppress the output if desired.

https://github.com/llvm/llvm-project/pull/68393