How to compile Android Application with system permissions

I need to compile an application with system permissions in order to use target application com.android.settings. For now while I try to run my apk I get the error message

Test run failed: Permission Denial: starting instrumentation ComponentInfo{com.jayway.test/android.test.InstrumentationTestRunner} from pid=354, uid=354 not allowed because package com.jayway.test does not have a signature matching the target com.android.settings

How can I compile my application with system permissions?

After having some search I found how to sign my application with system (platform) key. System signatures are located in directory <root-of-android-source-tree>/build/target/product/security. You can use them to sign your application with system privileges.

1. Add to manifest android:sharedUserId="android.uid.system"

2. Download System signatures files: platform.x509.pem platform.pk8

link: https://android.googlesource.com/platform/build/+/android-8.0.0_r17/target/product/security/

3. Sign app through terminal (java -jar signapk.jar platform.x509.pem platform.pk8 unsigned.apk signed.apk) (first you must put all files to one folder), or make certificate with keytool-importkeypair to make google_certificate.keystore and then

link for keytool-importkeypair download and explanation:

https://github.com/getfatday/keytool-importkeypair

4. After that steps install your signed system app to your device. Good luck!!!