[llvm] [SandboxVec] Boilerplate (PR #107431)

[Arthur Eubanks via llvm-commits]

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@@ -1,3 +1,5 @@
+add_subdirectory(SandboxVec)
+
 add_llvm_component_library(LLVMVectorize
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aeubanks wrote:

if we list the sources here we avoid a new component

https://github.com/llvm/llvm-project/pull/107431