This is a not per se request, but I was wondering if you avoided intentionally fully installing all necessary requirements for build.
Right now warmed image automatically downloads following:
Preparing "Install Android SDK Tools (revision: 26.1.1)".
"Install Android SDK Tools (revision: 26.1.1)" ready.
Installing Android SDK Tools in /opt/android/tools
"Install Android SDK Tools (revision: 26.1.1)" complete.
"Install Android SDK Tools (revision: 26.1.1)" finished.
Checking the license for package Android SDK Build-Tools 28.0.3 in /opt/android/licenses
License for package Android SDK Build-Tools 28.0.3 accepted.
Preparing "Install Android SDK Build-Tools 28.0.3 (revision: 28.0.3)".
"Install Android SDK Build-Tools 28.0.3 (revision: 28.0.3)" ready.
Installing Android SDK Build-Tools 28.0.3 in /opt/android/build-tools/28.0.3
"Install Android SDK Build-Tools 28.0.3 (revision: 28.0.3)" complete.
"Install Android SDK Build-Tools 28.0.3 (revision: 28.0.3)" finished.
Checking the license for package Android SDK Platform 28 in /opt/android/licenses
License for package Android SDK Platform 28 accepted.
Preparing "Install Android SDK Platform 28 (revision: 6)".
"Install Android SDK Platform 28 (revision: 6)" ready.
Installing Android SDK Platform 28 in /opt/android/platforms/android-28
"Install Android SDK Platform 28 (revision: 6)" complete.
"Install Android SDK Platform 28 (revision: 6)" finished.
Checking the license for package Android SDK Platform 30 in /opt/android/licenses
License for package Android SDK Platform 30 accepted.
Preparing "Install Android SDK Platform 30 (revision: 3)".
"Install Android SDK Platform 30 (revision: 3)" ready.
Installing Android SDK Platform 30 in /opt/android/platforms/android-30
"Install Android SDK Platform 30 (revision: 3)" complete.
"Install Android SDK Platform 30 (revision: 3)" finished.
Checking the license for package Android SDK Platform 29 in /opt/android/licenses
License for package Android SDK Platform 29 accepted.
Preparing "Install Android SDK Platform 29 (revision: 5)".
"Install Android SDK Platform 29 (revision: 5)" ready.
Installing Android SDK Platform 29 in /opt/android/platforms/android-29
"Install Android SDK Platform 29 (revision: 5)" complete.
"Install Android SDK Platform 29 (revision: 5)" finished.