driver: Set -DPROFILING when compiling C++ sources with profiling

Earlier, we used to pass all preprocessor flags to the c++ compiler.
This meant that -DPROFILING was passed to the c++ compiler because
it was a part of C++ flags
However, this was incorrect and the behaviour was changed in
8ff3134e. See #21291.

But that commit exposed this bug where -DPROFILING was no longer being passed
when compiling c++ sources.

The fix is to explicitly include -DPROFILING in `opt_cxx` when profiling is
enabled to ensure we pass the correct options for the way to both C and C++
compilers

Fixes #24286