[RISCV][test] Fix lifetime bug with Module in test

As pointed out by @s-barannikov in post-commit review of #72356, the
module is destroyed at the end of the constructor.

Author: asb

llvm/unittests/Target/RISCV/RISCVInstrInfoTest.cpp

@@ -31,6 +31,7 @@ class RISCVInstrInfoTest : public testing::TestWithParam<const char *> {
   std::unique_ptr<RISCVSubtarget> ST;
   std::unique_ptr<MachineModuleInfo> MMI;
   std::unique_ptr<MachineFunction> MF;
+  std::unique_ptr<Module> M;
 
   static void SetUpTestSuite() {
     LLVMInitializeRISCVTargetInfo();
@@ -49,10 +50,10 @@ class RISCVInstrInfoTest : public testing::TestWithParam<const char *> {
         CodeGenOptLevel::Default)));
 
     Ctx = std::make_unique<LLVMContext>();
-    Module M("Module", *Ctx);
-    M.setDataLayout(TM->createDataLayout());
+    M = std::make_unique<Module>("Module", *Ctx);
+    M->setDataLayout(TM->createDataLayout());
     auto *FType = FunctionType::get(Type::getVoidTy(*Ctx), false);
-    auto *F = Function::Create(FType, GlobalValue::ExternalLinkage, "Test", &M);
+    auto *F = Function::Create(FType, GlobalValue::ExternalLinkage, "Test", *M);
     MMI = std::make_unique<MachineModuleInfo>(TM.get());
 
     ST = std::make_unique<RISCVSubtarget>(