[clang] [memprof] Export __memprof_default_options_str on Darwin (PR #128920)

[Ellis Hoag via cfe-commits]

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@@ -1617,6 +1617,10 @@ void DarwinClang::AddLinkRuntimeLibArgs(const ArgList &Args,
     }
   }
 
+  if (Sanitize.needsMemProfRt())
+    if (hasExportSymbolDirective(Args))
+      addExportedSymbol(CmdArgs, "___memprof_default_options_str");
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ellishg wrote:

@teresajohnson I know you asked for this to be refactored into a constexpr string in a header, but I don't think `Darwin.cpp` and `MemProfiler.cpp` share any headers in common, so I don't know where I would put it. I don't think I can add `MemProfiler.h` to `Darwin.cpp` because it doesn't link in the `Instrumentation` component

https://github.com/llvm/llvm-project/pull/128920