Rollup merge of #104517 - dfordivam:patch-1, r=cuviper

Throw error on failure in loading llvm-plugin

The following code silently ignores the error as the `LLVMRustSetLastError` only tracks one error at a time. At all other places where `LLVMRustSetLastError` is used the code immediately returns.

https://github.com/rust-lang/rust/blob/251831ece9601d64172127b6caae9087358c2386/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp#L801-L804

compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp

@@ -800,7 +800,7 @@ LLVMRustOptimize(
       auto Plugin = PassPlugin::Load(PluginPath.str());
       if (!Plugin) {
         LLVMRustSetLastError(("Failed to load pass plugin" + PluginPath.str()).c_str());
-        continue;
+        return LLVMRustResult::Failure;
       }
       Plugin->registerPassBuilderCallbacks(PB);
     }