Build AOSP for Raspberry Pi 4 Under WSL2/Ubuntu 20.04

1_install_build_deps.sh

#!/bin/sh
sudo apt install -y \
    build-essential \
    gcc-arm-linux-gnueabihf \
    libssl-dev \
    flex \
    bison \
    python-mako \
    libncurses5 \
    libncurses5-dev \
    kpartx \
    curl \
    git

2_download_repo.sh

#!/bin/bash
mkdir -p ~/bin
curl https://storage.googleapis.com/git-repo-downloads/repo > ~/bin/repo
chmod a+x ~/bin/repo
echo Please add `$HOME/bin` to your $PATH variable

3_sync_code.sh

#!/bin/bash
case $1 in

# Android 10
  arpi-10)
  # For Chinese
  #repo init -u https://mirrors.tuna.tsinghua.edu.cn/git/AOSP/platform/manifest -b android-10.0.0_r41
  # For others
  repo init -u https://android.googlesource.com/platform/manifest -b android-10.0.0_r41
  git clone https://github.com/android-rpi/local_manifests .repo/local_manifests -b arpi-10
  ;;

# Android 11
  arpi-11)
  # For Chinese
  #repo init -u https://mirrors.tuna.tsinghua.edu.cn/git/AOSP/platform/manifest -b android-11.0.0_r33
  # For others
  repo init -u https://android.googlesource.com/platform/manifest -b android-11.0.0_r33
  git clone https://github.com/android-rpi/local_manifests .repo/local_manifests -b arpi-11
  ;;
  
  *)
  echo Usage $0 <arpi-10|arpi-11>
  ;;

esac

repo sync

4_build_kernel.sh

#!/bin/sh
export ARCH=arm
export CROSS_COMPILE=arm-linux-gnueabihf-
cd kernel/arpi
scripts/kconfig/merge_config.sh arch/arm/configs/bcm2711_defconfig kernel/configs/android-base.config kernel/configs/android-recommended.config
make zImage
make dtbs

5_build_android.sh

#!/bin/bash
source build/envsetup.sh
lunch rpi4-eng
make ramdisk systemimage vendorimage

6_mkimg.sh

#/bin/bash

DATE=`date +%Y%m%d`
IMGNAME=android-10-$DATE-rpi4.img
IMGSIZE=4
#OUTDIR=${ANDROID_PRODUCT_OUT:="../out/target/product/rpi4"}
OUTDIR="out/target/product/rpi4"

if [ `id -u` != 0 ]; then
	echo "Must be root to run script!"
	exit
fi

if [ -f $IMGNAME ]; then
	echo "File $IMGNAME already exists!"
else
	echo "Creating image file $IMGNAME..."
	dd if=/dev/zero of=$IMGNAME bs=1M count=$(echo "$IMGSIZE*1024" | bc)
	sync
	echo "Creating partitions..."
	(
	echo o
	echo n
	echo p
	echo 1
	echo
	echo +128M
	echo n
	echo p
	echo 2
	echo
	echo +1536M
	echo n
	echo p
	echo 3
	echo
	echo +256M
	echo n
	echo p
	echo
	echo
	echo t
	echo 1
	echo c
	echo a
	echo 1
	echo w
	) | fdisk $IMGNAME
	sync
	LOOPDEV=`kpartx -av $IMGNAME | awk 'NR==1{ sub(/p[0-9]$/, "", $3); print $3 }'`
	sync
	if [ -z "$LOOPDEV" ]; then
		echo "Unable to find loop device!"
		kpartx -d $IMGNAME
		exit
	fi
	echo "Image mounted as $LOOPDEV"
	sleep 5
	mkfs.fat -F 32 /dev/mapper/${LOOPDEV}p1 -n boot
	mkfs.ext4 /dev/mapper/${LOOPDEV}p2 -L system
	mkfs.ext4 /dev/mapper/${LOOPDEV}p3 -L vendor
	mkfs.ext4 /dev/mapper/${LOOPDEV}p4 -L userdata
	resize2fs /dev/mapper/${LOOPDEV}p4 1343228
	echo "Copying system..."
	dd if=$OUTDIR/system.img of=/dev/mapper/${LOOPDEV}p2 bs=1M
	echo "Copying vendor..."
	dd if=$OUTDIR/vendor.img of=/dev/mapper/${LOOPDEV}p3 bs=1M
	echo "Copying boot..."
	mkdir -p sdcard/boot
	sync
	mount /dev/mapper/${LOOPDEV}p1 sdcard/boot
	sync
	mkdir -p sdcard/boot/overlays
	cp device/arpi/rpi4/boot/* sdcard/boot/
	cp $OUTDIR/ramdisk.img sdcard/boot
	cp kernel/arpi/arch/arm/boot/zImage sdcard/boot/
	cp kernel/arpi/arch/arm/boot/dts/bcm2711-rpi-4-b.dtb sdcard/boot
	cp kernel/arpi/arch/arm/boot/dts//overlays/*.dtbo sdcard/boot/overlays
	cp kernel/arpi/arch/arm/boot/dts//overlays/README sdcard/boot/overlays
	sync
	umount /dev/mapper/${LOOPDEV}p1
	rm -rf sdcard
	kpartx -d $IMGNAME
	sync
	echo "Done, created $IMGNAME!"
fi

Place all scripts into $AOSP_DIR/scripts, then using:

$ ./scripts/1_install_build_deps.sh
$ ...