[clang] [clang] [hexagon] handle --unwindlib arg (PR #99552)

[Fangrui Song via cfe-commits]

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@@ -156,6 +156,8 @@ def err_drv_unsupported_rtlib_for_platform : Error<
   "unsupported runtime library '%0' for platform '%1'">;
 def err_drv_invalid_unwindlib_name : Error<
   "invalid unwind library name in argument '%0'">;
+def err_drv_unsupported_unwind_for_platform : Error<
+  "unwind library '%0' is not supported by this platform">;
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MaskRay wrote:

perhaps the message could be made more similar to `err_drv_unsupported_rtlib_for_platform`

https://github.com/llvm/llvm-project/pull/99552