[clang] [llvm] [PAC][Driver] Implement `-mbranch-protection=pauthabi` option (PR #97237)

[Fangrui Song via cfe-commits]

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@@ -1484,6 +1484,39 @@ void AddUnalignedAccessWarning(ArgStringList &CmdArgs) {
 }
 }
 
+static void handlePAuthABIOption(const ArgList &DriverArgs,
+                                 ArgStringList &CC1Args, const Driver &D) {
+  if (!DriverArgs.hasArg(options::OPT_fptrauth_intrinsics,
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MaskRay wrote:

See addOptInFlag.

But the implementation seems quite different from the title/description.

https://github.com/llvm/llvm-project/pull/97237