[clang] [clang] Enable descriptions for --print-supported-extensions (PR #66715)

[Balint Cristian via cfe-commits]

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@@ -22,7 +23,8 @@ struct RISCVExtensionInfo {
   unsigned MinorVersion;
 };
 
-void riscvExtensionsHelp();
+void getAllExtensions(StringMap<RISCVExtensionInfo> &Features);
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cbalint13 wrote:

It was men't as example. Anyway, prior certain versions (in our case 18) that accessor is still needed, won't go anywhere soon for compatibility.

https://github.com/llvm/llvm-project/pull/66715