Make it clear in the top-level Makefile how to configure mcuboot for
Zephyr for a particular signing algorithm. Currently supported, are the
RSA signatures, and ECDSA with the P-256 curve. These configuration
lines will select the code built in the bootloader, as well as which
public key gets included with the image.
This also adds a demo public key for the P-256 signatures.
Rather than commit our specific mbedtls config file into the Zephyr
tree, include it here, and add a path early in the make process so that
it will get picked up when building the library.
The Zephyr build systems makes some assumptions about the directory
layout, and encounters problems if the necessary path contains "../..".
To help this, place the zephyr directory next to the bootutil directory
so that the Makefile can just refer to "../bootutil". This keeps all of
the build artifacts under the proper top-level directory.
The Zephyr build system does strange things if it refers to source
directories above the main Makefile (generating
outdir/<target>/../boot/... paths). For now, fix this by moving the
Zephyr Makefile to the top-level in the tree. This shouldn't have much
impact on Mynewt, as it doesn't use makefiles.
David Brown