[flang][driver] Add checks for missing option arguments

With this patch, the following invocation of the frontend driver will
return an error:
```
flang-new -fc1 input-file.f90 -o
```
Similar logic applies to other options that require arguments.

Similar checks are already available in the compiler driver, flang-new
(that's implemented in clangDriver).

Differential Revision: https://reviews.llvm.org/D103554