[clang] [Clang] Make `-Xarch_` handling generic for all toolchains (PR #125421)

[Artem Belevich via cfe-commits]

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@@ -932,7 +932,9 @@ def W_Joined : Joined<["-"], "W">, Group<W_Group>,
 def Xanalyzer : Separate<["-"], "Xanalyzer">,
   HelpText<"Pass <arg> to the static analyzer">, MetaVarName<"<arg>">,
   Group<StaticAnalyzer_Group>;
-def Xarch__ : JoinedAndSeparate<["-"], "Xarch_">, Flags<[NoXarchOption]>;
+def Xarch__ : JoinedAndSeparate<["-"], "Xarch_">, Flags<[NoXarchOption]>,
+  HelpText<"Pass <arg> to the compiliation if the target matches <arch>">,
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Artem-B wrote:

We do need a better documentation. It's not obvious that <arch> could be a GPU name or an arch name from the target triple.

https://github.com/llvm/llvm-project/pull/125421