First checkout minimal twrp with omnirom tree:
repo init -u git://github.com/minimal-manifest-twrp/platform_manifest_twrp_omni.git -b twrp-8.1
repo sync
Then add these projects to .repo/manifest.xml:
<project path="device/sony/akari" name="MartinX3/android_device_sony_akari" remote="github" revision="android-9.0" />To make all works you need to modify the buildinfo.sh in build/tools
echo "ro.build.version.release=$PLATFORM_VERSION"
echo "ro.build.version.security_patch=$PLATFORM_SECURITY_PATCH"
to
echo "ro.build.version.release_orig=$PLATFORM_VERSION"
echo "ro.build.version.security_patch_orig=$PLATFORM_SECURITY_PATCH"
And you need to increase the PLATFORM_VERSION to 16.1.0 in build/core/version_defaults.mk to override Google's anti-rollback features
Finally execute these:
. build/envsetup.sh export ALLOW_MISSING_DEPENDENCIES=true # Only if you use minimal twrp tree. lunch omni_akari-eng mka adbd bootimage
To test it:
fastboot boot out/target/product/akari/boot.img