[ahlCVA]

Buildroot has package-parallel builds when using BR2_PER_PACKAGE_DIRECTORIES (see https://buildroot.org/downloads/manual/manual.html#top-level...). It's for some reason still marked as experimental in the docs but it has been solid for me for many years.

The lack of dependency tracking isn't great but other than working around it like you described just using ccache has worked pretty well for me. My Buildroot images at work do full recompiles in under 10 minutes that way.

Meanwhile the Yocto projects I've worked on used to have a ton of chaff that causes partial rebuilds with trivial changes to take longer than that. This probably isn't an inherent Yocto/BitBake thing but the majority of Yocto projects out there seems to take a very kitchen-sink approach so it's what you'll end up having to deal with in practice.