Cross Compiling Bare-Metal systems

Most bare-metal systems follow the Linux tradition:
The "CROSS_COMPILE" variable sets the prefix
The "ARCH" variable sets the top-level subtree

Also, most bare-metal systems are based on Kconfig
You can "make defconfig" (depends on $ARCH)
Mode defaults live in the configs/ subdir
You can interactively change the configuration
"make config", "make oldconfig", "make menuconfig", ...

The current configuration lives in .config (the output of configuring)
This is an input file for make
A corresponding header is generated for C language

One problem with Kconfig is reproducing a build
If it can fit, it makes sense to save .config in the binary
This in addiion to the build commit, a mandatory item

Please consider setting up reproducible builds for your own OS