[clang] Fix build break in SemaHLSL.cpp on MSVC 2022: warning C4715: 'getResourceClass': not all control paths return a value (PR #112767)

[Aaron Ballman via cfe-commits]

================
@@ -102,6 +102,7 @@ static ResourceClass getResourceClass(RegisterType RT) {
     return ResourceClass::Sampler;
   case RegisterType::C:
   case RegisterType::I:
+  default:
     llvm_unreachable("unexpected RegisterType value");
   }
----------------
AaronBallman wrote:

> As a compromise we could keep the unreachable at the bottom, and then deliberately fall through to that in the unhandled cases:

FWIW, that's the usual approach we take.

https://github.com/llvm/llvm-project/pull/112767