[clang] Enable unique-object-duplication warning for windows (PR #143537)

[Devon Loehr via cfe-commits]

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@@ -806,7 +806,9 @@ def UniqueObjectDuplication : DiagGroup<"unique-object-duplication"> {
 Warns when objects which are supposed to be globally unique might get duplicated
 when built into a shared library.
 
-If an object with hidden visibility is built into a shared library, each instance
+This can occur to objects which are hidden from the dynamic linker, due to
+having hidden visibility (on posix) or lacking an import/export annotation (on
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DKLoehr wrote:

Done.

https://github.com/llvm/llvm-project/pull/143537