Tests: cover testing multiple async executable targets

[kateinoigakukun]

Test apple/swift#69113: [Concurrency] Hide async_Main from other object files

Merge after the above fix will be merged

Motivation:

To verify that multiple executable targets with async entrypoints can be linked within a single test executable

Resolves rdar://114231968

Modifications:

Added a new test case

[neonichu]

Thanks!

[kateinoigakukun]

@swift-ci Please smoke test

[MaxDesiatov]

@swift-ci test

[neonichu]

I guess we need some way to skip these tests in the self-hosted environment, because they won't have a new enough compiler any time soon.

[kateinoigakukun]

@neonichu I don't have a good and stable idea to detect if the given swift-frontend has the fix or not 🤔 I think we can wait to merge this until the next nightly toolchain will be shipped.

[kateinoigakukun]

Ah, it looks like macOS self-hosted CI uses Xcode toolchain, so just waiting the next nightly doesn't work.

[MaxDesiatov]

Yeah, "next" here means next version of Xcode, for which we can't provide a schedule.

[MaxDesiatov]

Maybe tests could be gated on the version of Swift, 5.10 I guess?

[kateinoigakukun]

The async version test is split out from the sync version and guarded by #if compiler(<5.10). I think this should work without waiting for the next Xcode update in the CI and just need to wait for the next Linux nightly toolchain.

[neonichu]

@swift-ci test

[kateinoigakukun]

@swift-ci test

[neonichu]

I believe Linux self-hosted uses a nightly toolchain, so we have to wait until that contains the compiler changes.

[MaxDesiatov]

@swift-ci test linux