TARGET_CPU_VARIANT not set or set to an unknown value

[test-in-prod]

Hey, trying to adapt your sources to Doogee S90 which runs the same CPU and seems to follow similar EMMC partition layout. However, I am completely new to building TWRP from scratch. I think I got the environment setup right, and I think I got the right recovery.fstab from the stock recovery and just had to adjust a few things.

Anyway, trying to build with command mka recoveryimage all I get is this:

bionic/libc/arch-arm64/arm64.mk:65: *** "TARGET_CPU_VARIANT not set or set to an unknown value. Possible values are generic, denver64. Use generic for devices that do not have a CPU similar to any of the supported cpu variants.".
build/core/ninja.mk:172: recipe for target '/mnt/c/temp/DS90/TWRPKitchen/android_device_doogee_S90/out/build-omni_fiona.ninja' failed
make: *** [/mnt/c/temp/DS90/TWRPKitchen/android_device_doogee_S90/out/build-omni_fiona.ninja] Error 1

Is there anything else I need?