[EmitC] Fix error message in compiler driver (#16727)

compiler/src/iree/compiler/API/Internal/CompilerDriver.cpp

diff --git a/compiler/src/iree/compiler/API/Internal/CompilerDriver.cpp b/compiler/src/iree/compiler/API/Internal/CompilerDriver.cpp
index 26beb37..9792e9f 100644
--- a/compiler/src/iree/compiler/API/Internal/CompilerDriver.cpp
+++ b/compiler/src/iree/compiler/API/Internal/CompilerDriver.cpp
@@ -1033,7 +1033,7 @@
     parsedModule->emitError() << "expected a vm.module or builtin.module";
   }
   if (failed(result)) {
-    return new Error("failed to generate bytecode");
+    return new Error("failed to generate C source code");
   }
   output.outputStream->flush();
   return output.getWriteError();