cmake: add tfm / tfa image information to build info

Support for list of images in build info was added with commit
4061311d and is used by sysbuild.

Zephyr itself also uses CMake's External Project feature when including
TF-M or TF-A in a Zephyr build.

Populate build info with TF-M / TF-A information when said image is
included in the build.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>