[mlir][target] RAII wrap moduleToObject timer to ensure call clear function (llvm#136142)

As title, we need to call `Timer::clear` to avoid extra log like this:
```
===-------------------------------------------------------------------------===
                           ...
===-------------------------------------------------------------------------===
  Total Execution Time: 0.0000 seconds (0.0000 wall clock)

   ---Wall Time---  --- Name ---
        -----       ....
        -----       Total
```

Author: MikaOvO

mlir/lib/Target/LLVM/NVVM/Target.cpp

@@ -26,6 +26,7 @@
 #include "mlir/Target/LLVMIR/Dialect/NVVM/NVVMToLLVMIRTranslation.h"
 #include "mlir/Target/LLVMIR/Export.h"
 
+#include "llvm/ADT/ScopeExit.h"
 #include "llvm/Config/llvm-config.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/FileUtilities.h"
@@ -673,6 +674,7 @@ NVPTXSerializer::moduleToObject(llvm::Module &llvmModule) {
   llvm::Timer moduleToObjectTimer(
       "moduleToObjectTimer",
       "Timer for perf llvm-ir -> isa and isa -> binary.");
+  auto clear = llvm::make_scope_exit([&]() { moduleToObjectTimer.clear(); });
   // Return LLVM IR if the compilation target is `offload`.
 #define DEBUG_TYPE "serialize-to-llvm"
   LLVM_DEBUG({