Extract sros_artifacts fixture into a CMake script

[cottsay]

All of these commands should be run together to set up the fixture for the tests. When running tests with repitition, we want to run through the entire artifact setup and not run each individual command multiple times.

Fixes #522

CI, using --retest-until-fail 2:

• Linux
• Linux-aarch64
• Windows

[clalancette]

If I understand this properly, then we are essentially treating sros_artifacts.cmake as a test script and executing the entirety of it before each test invocation. Is that correct?

Could we also make this test an e.g. Python script instead? I actually don't care that much whether we keep this as CMake or a script, but I just wanted to mention that as a possibility.

[cottsay]

Is that correct?

Correct. In the presence of --retest-until-fail, the entire script will be run multiple times instead of the previous behavior, where each command was run multiple times.

Could we also make this test an e.g. Python script instead?

Absolutely - it's just easier to use CMake since that's what we're already using, rather than finding the Python executable to invoke a Python script.

[clalancette]

Thanks for the quick fix!