[llvm] [LV] Nest cl::opts under namespace llvm (NFC) (PR #221891)

[Florian Hahn via llvm-commits]

================
@@ -51,6 +51,9 @@
 
 namespace llvm {
 
+LLVM_ABI extern cl::opt<unsigned> NumberOfStoresToPredicate;
+LLVM_ABI extern cl::opt<bool> VPlanBuildOuterloopStressTest;
----------------
fhahn wrote:

Are those good examples for that rational? IIRC they are needed in the header, because they are used by `runPass`, which is defined in the header

https://github.com/llvm/llvm-project/pull/221891