[llvm] [Hexagon] Add missing build attributes (PR #166992)

[Ikhlas Ajbar via llvm-commits]

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@@ -311,6 +311,12 @@ static std::optional<std::string> hexagonAttrToFeatureString(unsigned Attr) {
     return "v73";
   case 75:
     return "v75";
+  case 77:
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iajbar wrote:

Should V77 be removed?

https://github.com/llvm/llvm-project/pull/166992