shit here could be wrong/misleading; take all this with a grain of salt.

rule overrides seem to be errors now

dexpreopt_bootjars has now moved to the soong build system

All modules to be added as bootjars need to migrate to Android.bp rules

They also need to be marked as installable

installable: true,

Else they aren't picked up for bootjar dexpreopt at all

Also, much like last time, snooping around base, SystemUI and Settings, doesn't look like Google pushed any major visual changes on the preview tag.

You can add

BUILD_BROKEN_DUP_RULES := true

to work around this for the time being.
But yeah, if you have this, I guess it's time to fix your build rules.

Similarly,

BUILD_BROKEN_PHONY_TARGETS := true

Particularly useful if you're trying to use the current kernel.mk rules. Again, this should be fixed up properly and this is a mere workaround.
Google was nice enough to "warn" us this way, I guess 😆

Oh I should probably add in a few older findings here too

soong json generation has improved a lot since pie. There are now saner functions to handle this. For reference, see this.
So, now our custom map's config.mk would looks something like this:
https://github.com/PotatoProject-next/vendor_potato/commit/6ca5af3c9647898ea60feab9c8711fa64333aa06

Oh also, if you come across a build error on libselinux, this should fix it:
https://github.com/PotatoProject-next/external_selinux/commit/b4177583030e8e6a16f8976c570562d319ce5a1b
Not sure if this is the right thing to do, but it at least gets things going.

Most are probably aware, but yeah. Might as well add it here.
add_lunch_combo is deprecated and lunch relies on a build var:
Set COMMON_LUNCH_CHOICES in your AndroidProducts.mk, instead.

Also, AOSP now has fuchsia targets 😆

Thank you Google, very cool.

Checking the PATH variable from make, there seems to be only
/home/agentfabulous/q-preview/prebuilts/build-tools/path/linux-x86:/home/agentfabulous/q-preview/out/.path by default.
/home/agentfabulous/q-preview/out/.path has symlinks to ../.path_interposer

I don't know what I was expecting, but yes the only differnce now is that the system PATH variable is no more considered at all. We need to add paths to prebuilt binaries in our kernel.mk or we can look into path_interposer's inclusions.

So, path_interposer will back up the current PATH data to a file in outdir. This is restored when soong is exiting. If you manage to kill soong during the build (or even hit Ctrl+c a bunch of times when it starts exiting from the initial interrupt), you'll be left with the PATH set for the build.

inline kernel compilation now works :)