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

[Peter Smith via cfe-commits]

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@@ -1484,6 +1484,39 @@ void AddUnalignedAccessWarning(ArgStringList &CmdArgs) {
 }
 }
 
+static void handlePAuthABIOption(const ArgList &DriverArgs,
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smithp35 wrote:

I think it will be worth a comment above and possibly inline explaining the ABI implications of the options.

For example:
```
Each combination of options here forms a signing schema, and in most cases each signing schema is its own incompatible ABI. The default values of the options represent the default signing schema.
```



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