Use archlinux/base as parent image

[iqqmuT]

pritunl/archlinux is no longer maintained so changing the base image.

Pacman got random errors when downloading packages from https://farwayer.keybase.pub/. Changing pacman to use wget as downloader fixed that problem.

Also latest Android SDK Build Tools 28.0.3 added.

Fixes #3

[farwayer]

@iqqmuT thank you for PR! What about adding procps-ng? For?

[iqqmuT]

procps-ng provides sysctl tool which is also pre-installed in pritunl/archlinux image.

I added it because I am using this Docker image with GitLab CI and I wanted to be able to run command

sysctl fs.inotify.max_user_watches=524288

to get around this issue: facebook/watchman#163

However, sysctl is not required, an alternative way to achieve the same result is:

echo 524288 | tee /proc/sys/fs/inotify/max_user_watches

So, do you suggest me to drop procps-ng package away?