[clang] [PAC][Driver] Enable BTI and PAC by default on OpenBSD/aarch64 (PR #125392)

[Fangrui Song via cfe-commits]

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@@ -1582,7 +1588,10 @@ static void CollectARMPACBTIOptions(const ToolChain &TC, const ArgList &Args,
       D.Diag(diag::err_drv_unsupported_option_argument)
           << A->getSpelling() << Scope;
     Key = "a_key";
-    IndirectBranches = false;
+    if (Triple.isOSOpenBSD() && isAArch64)
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MaskRay wrote:

IndirectBranches = Triple.isOSOpenBSD() && isAArch64

https://github.com/llvm/llvm-project/pull/125392