Using a custom patch against MicroPython's CMakeLists.txt this will
optionally use a memmap_mp.ld file from the *board* directory and
allow us to check if the allocated app flash overflows.
Linker scripts need configured on a per board basis.
Add a patch for CMakeLists.txt which adds -Wl,--print-memory-usage so
we can get at least some useful information about which builds are
running close to the limits.