[llvm] [NFC] [docs] point users towards clang remark flags (PR #147820)

[Florian Hahn via llvm-commits]

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@@ -57,6 +57,11 @@ Enabling optimization remarks
 There are two modes that are supported for enabling optimization remarks in
 LLVM: through remark diagnostics, or through serialized remarks.
 
+See also the clang flags
+`-Rpass <https://clang.llvm.org/docs/UsersManual.html#options-to-emit-optimization-reports>`_
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fhahn wrote:

Is it possible to directly reference the sections via RST, so we don't hard-code them? This would avoid potentially having them broken in the future.

If not, that should be fine.

https://github.com/llvm/llvm-project/pull/147820