[llvm] [CodingStandard] Rework anonymous namespace section to cover visibility more broadly (PR #126775)

[Rahul Joshi via llvm-commits]

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@@ -1640,6 +1640,10 @@ you have no immediate way to tell if this function is local to the file.  In
 contrast, when the function is marked static, you don't need to cross-reference
 faraway places in the file to tell that the function is local.
 
+Related to this issue, when non-member functions or variables are defined in a
+`.cpp`` file and need not be referenced outside that file, make them `static`.
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jurahul wrote:

Finally got around to updating this based on the suggestion above. @AaronBallman and @joker-eph PTAL.

https://github.com/llvm/llvm-project/pull/126775