Generate a signed apk from decompiled smali sources (with a tool like apktool)

build-n-sign.sh

#!/bin/sh

BUILD_TOOLS=$HOME/Android/Sdk/build-tools/32.1.0-rc1
PATH="$PATH:$BUILD_TOOLS"
KEY="$PWD/key.jks"

if [ ! -f $KEY ]; then
    echo "No keystore found in Working Directory. Creating a new one. Please fill the prompts, or cancel and copy your keystore file to $KEY."
    keytool -genkey -v -keystore key.jks -keyalg RSA -keysize 2048 -validity 10000 -alias apk
fi

##clean
echo Cleaning...
rm -rf dist/*

##repack
echo Repacking...
apktool b .

APK=$(ls -1 dist | head -n 1)

echo Aligning...
zipalign 4 -f ./dist/$APK ./dist/out-$APK
echo Signing...
apksigner sign --ks key.jks ./dist/out-$APK
echo Done: out-$APK