[llvm] [CodeGen] Let `PassBuilder` support machine passes (PR #76320)

[Arthur Eubanks via llvm-commits]

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@@ -463,8 +463,7 @@ class LLVMTargetMachine : public TargetMachine {
   }
 
   virtual std::pair<StringRef, bool> getPassNameFromLegacyName(StringRef) {
-    llvm_unreachable(
-        "getPassNameFromLegacyName parseMIRPipeline is not overridden");
+    llvm_unreachable("getPassNameFromLegacyName is not overridden");
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aeubanks wrote:

please submit this change separately (no review required)

https://github.com/llvm/llvm-project/pull/76320