The mallopt symbol is defined in tiny-malloc.c, not mallocr.c, but
the Makefile in here tries to compile it out of the latter. This
leads to mallopt never being defined.
The build also creates mallinfo.o & mallopt.o & mallstats.o objects
to override common ones, but the common dir doesn't use these names.
Instead, it places these all in mstats.o.
So move the build define logic to a dedicated file and compile it
directly to make things a bit simpler while fixing the missing func
and aligning objects with the cmomon code.