Added Integration Tests to Buildkite Pipeline

[larryk85]

Change Description

This pull request is a culmination of three related changes.

Integration Tests

When CDT is built in the presence of EOSIO, which itself has been built and installed from source, the CDT build generates additional integration tests. I have added steps to the CDT Buildkite pipeline to build in the presence of EOSIO and run these integration tests.

These changes rely upon the dependencies file in the root of CDT, and upon the tests registered with ctest being labeled. Thus, I have added a dependencies file exactly like the one in eosio.contracts, and added test labels.

Pipeline Configuration File

I have added the universal pipeline configuration file, pipeline.jsonc, described in pull request 512 and auto-buildkite-pipelines pull request 99. This replaces the dependencies file described above.

sccache Support

I have added support for sccache to accelerate CDT build times in Buildkite. I also added support for sccache to EOSIO LLVM in pull request 23, but Larry has asked me to hold off on updating the submodule as a part of this pull request because of work John is doing. We will merge this pull request as-is, and the submodule will get updated later.

Tested

Base Case (original pipeline):

• Build 197
• Build 194 against Ubuntu 18.04 only

New Pipeline:

• Build 252 with integration tests
• Build 307 without integration tests or sccache
• Build 389 with sccache

You can see in build 252 that CDT integration tests run correctly but are failing. They are currently disabled by default in the pipeline, but are supported and can be run using:
New Build > Options > Environment Variables > SKIP_INTEGRATION_TESTS='false'

API Changes

• API Changes
  None.

Documentation Additions

• Documentation Additions
  None.