Added build-secp256k1.sh for running secp tests in TeamCity

Summary:
Allows us to test secp builds which currently do not run on TeamCity
Depends on D2717
Depends on D2685 only to get passing tests

TeamCity images have been updated to include the jdk 8 dependency.

Test Plan:

sudo apt-get install openjdk-8-jdk # dependencies to build and run the java tests
./contrib/teamcity/build-secp256k1.sh

This fails as expected without D2685 applied and passes with D2685 applied.
Tested on a TeamCity agent instance and locally.

Reviewers: #bitcoin_abc, deadalnix, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien, teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2686