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

[Vincent Lee 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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thevinster wrote:

What did you mean by optional here? Like a CMake flag that enables the message? In general, I find this message to be quite helpful when debug whether targets were applied with custom flags without needing to go into the CMakeCache.txt. 

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