What worked for me was:

android list sdk -a

Which showed me the following list:

1- Android SDK Tools, revision 24.0.22- Android SDK Platform-tools, revision 213- Android SDK Build-tools, revision 21.1.24- Android SDK Build-tools, revision 21.1.15- Android SDK Build-tools, revision 21.16- Android SDK Build-tools, revision 21.0.27- Android SDK Build-tools, revision 21.0.1... and a great many more

Followed by the command:

android update sdk -a -u -t 3

The "3" in the command refers the the index listed in the output of the first command.

Solved it by using

android update sdk -u -a

where the a parameter installs all packages. Not the best solution to install everything, but it has at least installed the required build tools version

I was getting this error on my Jenkins too:

failed to find Build Tools revision 21.1.2

Instead of getting all Android SDK updates, I just needed to:

Get Build Tools revision 21.1.2

sudo android update sdk --no-ui --all --filter build-tools-21.1.2

Other commands I've used:

Help:

sudo android update sdk --help

Get list of available Android SDK updates:

sudo android list sdk --extended --all