Howdy, @jjsuwa! Looks good if a bit pedantic (dropping casts).

Let me do a couple checks on real HW just to verify the a14 change.

In the meantime, this file comes from upstream in the newlib toolchain. Can you put in the same PR there? https://github.com/earlephilhower/newlib-xtensa

OTW, this change will be lost as soon as a new toolchain build is done.