[mlir] Fix ignoring return value warning for Toy CLIs

After [the change](https://github.com/llvm/llvm-project/commit/470f3cee3557974bb1820722bf82d86b8909199b) returning LogicalResult from applyPassManagerCLIOptions, the warning message is shown in the Toy CLIs saying it's not using the returned values. We can check the result and return non-zero value as the pass failure.

```
/Users/sasaki/dev/llvm-project/mlir/examples/toy/Ch3/toyc.cpp:118:5: warning: ignoring return value of function declared with 'nodiscard' attribute [-Wunused-result]
    applyPassManagerCLOptions(pm);
    ^~~~~~~~~~~~~~~~~~~~~~~~~ ~~
1 warning generated.
[473/485] Building CXX object tools/mlir/examples/toy/Ch4/CMakeFiles/toyc-ch4.dir/toyc.cpp.o
/Users/sasaki/dev/llvm-project/mlir/examples/toy/Ch4/toyc.cpp:119:5: warning: ignoring return value of function declared with 'nodiscard' attribute [-Wunused-result]
    applyPassManagerCLOptions(pm);
    ^~~~~~~~~~~~~~~~~~~~~~~~~ ~~
1 warning generated.
[477/485] Building CXX object tools/mlir/examples/toy/Ch5/CMakeFiles/toyc-ch5.dir/toyc.cpp.o
/Users/sasaki/dev/llvm-project/mlir/examples/toy/Ch5/toyc.cpp:122:3: warning: ignoring return value of function declared with 'nodiscard' attribute [-Wunused-result]
  applyPassManagerCLOptions(pm);
  ^~~~~~~~~~~~~~~~~~~~~~~~~ ~~
1 warning generated.
[479/485] Building CXX object tools/mlir/examples/toy/Ch6/CMakeFiles/toyc-ch6.dir/toyc.cpp.o
/Users/sasaki/dev/llvm-project/mlir/examples/toy/Ch6/toyc.cpp:139:3: warning: ignoring return value of function declared with 'nodiscard' attribute [-Wunused-result]
  applyPassManagerCLOptions(pm);
  ^~~~~~~~~~~~~~~~~~~~~~~~~ ~~
1 warning generated.
[481/485] Building CXX object tools/mlir/examples/toy/Ch7/CMakeFiles/toyc-ch7.dir/toyc.cpp.o
/Users/sasaki/dev/llvm-project/mlir/examples/toy/Ch7/toyc.cpp:139:3: warning: ignoring return value of function declared with 'nodiscard' attribute [-Wunused-result]
  applyPassManagerCLOptions(pm);
  ^~~~~~~~~~~~~~~~~~~~~~~~~ ~~
1 warning generated.
```

Reviewed By: mehdi_amini

Differential Revision: https://reviews.llvm.org/D147402