[MLton] fixing -codegen c -profile time for the release

[Florian Weimer]

> The code is always a member of a C++ class
> virtual non-static member function, and it is not
> called in the same compilation unit, the only calls
> are made in a different compilation unit via virtual
> dispatch. In fact .. the code lives in shared library
> by default and is called by a driver program that
> dlopen() it.. so not even the linker could inline it.

The GCC people are working on whole-program optimization,
devirtualization (even profile-guided partial variants) and other
magic.  It will become more and more difficult to outguess the
optimizers. 8-)