Downloading the Android support library from command line

sdkmanager "extras;android;m2repository"

worked for me.
I ran in to the error: Warning: File /var/root/.android/repositories.cfg could not be loaded.

so I had to create that file before running the above command.

touch ~/.android/repositories.cfg

echo y | android update sdk --no-ui --all --filter "extra-android-m2repository"

android command is deprecated now

You can use sdkmanager instead like so:

sdkmanager --install "extras;android;m2repository"