[clang] [clang][PAC] add support for options parameter to __ptrauth (PR #136828)

[Aaron Ballman via cfe-commits]

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@@ -65,6 +65,17 @@ enum class PointerAuthenticationMode : unsigned {
   SignAndAuth
 };
 
+static constexpr llvm::StringLiteral PointerAuthenticationOptionStrip = "strip";
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AaronBallman wrote:

> I was meaning "is there a more idiomatic way to have these string constants specified?" :D

Usually we'd do what @erichkeane was suggesting -- not have these as constants in LangOptions.h but instead have helper functions which convert string -> enum -> string. Then these strings can be hidden within a .cpp file rather than exposed in a header with broader visibility. WDYT?

https://github.com/llvm/llvm-project/pull/136828