Add a lit test for Xcode project generation

[AnthonyLatsis]

The test takes ~100s on my machine.

Changes to CMake code tend to break Xcode project generation every other month or so. Although these issues are often fixed in a matter of days and are not as big of a deal for seasoned contributors, Xcode is the editor of choice for many, if not most, newcomers, and I believe this makes un interested in promising a functional invocation with the Xcode version used in CI.

[AnthonyLatsis]

@swift-ci please smoke test macOS

[AnthonyLatsis]

186.43s: Swift-validation(macosx-x86_64) :: BuildSystem/generate_xcode.test

[ahoppen]

Nice. 3 minutes is really good. Let’s add this.

[ahoppen]

I’m not sure why we used to add the clean target but it looks like we lost it. Is that intentional?

[AnthonyLatsis]

Neither am I, but I doubt it makes a difference.

Is that intentional?

Yes, I changed the logic slightly to not run any build commands for LLVM when --build-llvm=0 (the "actually don’t build LLVM" option), so it no longer matters what build_targets is set to in this case. This behavior is consistent with how we handle other CMake products, and it allows the new test to not just succeed (a build command that was assembled for the Xcode generator will fail against a Ninja build directory due to incompatible adjustments to the options), but also run correctly (we don’t want to run any build commands against the symlinked LLVM build directory).

[ahoppen]

Sounds reasonable to me 👍🏽

[AnthonyLatsis]

@swift-ci please smoke test macOS

[AnthonyLatsis]

Hm, it seems like none of the macOS PR testing jobs run long tests. I can only see select branch jobs running them. Do we keep the requirement?

[ahoppen]

Let’s make it a non-long test then, I’d say.

[AnthonyLatsis]

@swift-ci please smoke test macOS

[AnthonyLatsis]

@shahmishal ping

[shahmishal]

@swift-ci smoke test

[xedin]

LGTM!