Several small improvements to build-script-helper.py

[ahoppen]

This PR contains a set of small improvements to build-script-helper.py, including the one from #91.

• Add argument to build-script-helper.py to update SwiftPM dependencies
• Fail with an error message instead of a stack trace when a subcommand failed
• Don't run build action if a test is requested
  • The test action creates its own build and building twice just wastes resources.
• Name generated SwiftEvolve project SwiftEvolve
  • Previously also the generated SwiftEvolve Xcode projects was named SourceKitStressTester
• Update .gitignore in SwiftEvolve to match the one in the stress tester

[beccadax]

• Don't run build action if a test is requested

Does build-script ask us to just test when it assumes that this will also cause a build? If so, this may not be the right move.

[ahoppen]

Does build-script ask us to just test when it assumes that this will also cause a build? If so, this may not be the right move.

swift test always creates its own build. And since it’s using a different build directory it cannot reuse the build that was already created beforehand, effectively doubling the test time.

[ahoppen]

CI testing passed: https://ci.swift.org/job/swift-PR-osx-preset/64/

[nathawes]

LGTM!

[nathawes]

Not important, but you could return "all" in selected_actions at this point, or replace the whole body with something like return any(item in (action_name, "all") for item in selected_actions).

[ahoppen]

I actually find it clearer this way. The second suggestion means, I actually need to think about what’s going on and I like repeating the same pattern that I used for action_name already for "all". It’s a bit more verbose but I find it reads clearer.

[nathawes]

No worries!