So far it consists of following builds:
- GCC 9.1 (Ubuntu 18.04)
- GCC 8.3 (Ubuntu 18.04)
- GCC 7.4 (Ubuntu 18.04 default)
- GCC 5.4 (Ubuntu 16.04 default)
- Clang 10.0 (macOS 10.14 Mojave default)
- Clang 6.0 (Ubuntu 18.04)
Workflow also defines static code analysis using Clang 6 (Ubuntu 18.04),
which does not indicate results directly in PRs yet, but uploads a
static analysis report as a build artifact.