[mlir] Update signal failure error message

User was confused by previous wording when pass was reported as failing
due to signal in unrelated thread being caught.

Differential Revision: https://reviews.llvm.org/D145213

mlir/lib/Pass/PassCrashRecovery.cpp

@@ -158,8 +158,8 @@ void RecoveryReproducerContext::crashHandler(void *) {
 
     // Emit an error using information only available within the context.
     emitError(context->preCrashOperation->getLoc())
-        << "A failure has been detected while processing the MLIR module:"
-        << description;
+        << "A signal was caught while processing the MLIR module:"
+        << description << "; marking pass as failed";
   }
 }