[llvm] [LLVM][runtimes] Prepopulate `LLVM_BUILTIN_TARGETS` with runtimes values (PR #95554)

[Petr Hosek via llvm-commits]

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@@ -17,7 +17,11 @@ foreach(proj ${LLVM_ENABLE_RUNTIMES})
 endforeach()
 
 function(get_compiler_rt_path path)
-  foreach(entry ${runtimes})
+  set(all_runtimes ${runtimes})
+  foreach(name ${LLVM_RUNTIME_TARGETS})
+    list(APPEND all_runtimes RUNTIMES_${name}_LLVM_ENABLE_RUNTIMES)
+  endforeach()
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petrhosek wrote:

You should consider deduplicating the items in the list here:
```suggestion
  endforeach()
  list(REMOVE_DUPLICATES all_runtimes)
```

https://github.com/llvm/llvm-project/pull/95554