[flang][mlir] disable mlir threading

Author: ronlieb

mlir/lib/IR/MLIRContext.cpp

@@ -59,7 +59,8 @@ struct MLIRContextOptions {
   llvm::cl::opt<bool> disableThreading{
       "mlir-disable-threading",
       llvm::cl::desc("Disable multi-threading within MLIR, overrides any "
-                     "further call to MLIRContext::enableMultiThreading()")};
+                     "further call to MLIRContext::enableMultiThreading()"),
+      llvm::cl::init(true)};
 
   llvm::cl::opt<bool> printOpOnDiagnostic{
       "mlir-print-op-on-diagnostic",

mlir/test/Pass/invalid-pass.mlir

@@ -1,5 +1,5 @@
 // RUN: not mlir-opt %s -pass-pipeline='builtin.module(builtin.module(test-module-pass{test-option=a}))' 2>&1 | FileCheck %s
-// RUN: not mlir-opt %s -mlir-print-ir-module-scope -mlir-print-ir-before=cse 2>&1 | FileCheck -check-prefix=PRINT_MODULE_IR_WITH_MULTITHREAD %s
+// RUN: not mlir-opt %s -mlir-disable-threading=0 -mlir-print-ir-module-scope -mlir-print-ir-before=cse 2>&1 | FileCheck -check-prefix=PRINT_MODULE_IR_WITH_MULTITHREAD %s
 
 // CHECK: <Pass-Options-Parser>: no such option test-option
 // CHECK: failed to add `test-module-pass` with options `test-option=a`