Track down "the textual interface may be broken by project issues or a compiler bug" (wip)

[weliveindetail]

We don't yet build the Android SDK with the Windows toolchain continuously. This issue came up in a recent PR:

T:/x64/Android.platform/Developer/SDKs/Android.sdk\usr\lib\swift\android\Synchronization.swiftmodule\x86_64-unknown-linux-android.private.swiftinterface:5:8:
error: failed to build module 'Android' for importation due to the errors above;
the textual interface may be broken by project issues or a compiler bug

Attaching the full log here: swift-PR-windows-37178-android.log Let's try and track this down in isolation.

[weliveindetail]

First, let's make sure this reproduces on mainline for the aarch64 SDK without my testing patches

swiftlang/swift-testing#944
swiftlang/swift-corelibs-foundation#5166
@swift-ci please test Windows

[weliveindetail]

Yes, it reproduces the issue!

Here is the last working state I found so far:

swift c2e36decfe4cb91db53baf01a1daa94c84e7ebcc (Feb 16)
llvm-project a3e32cdaae72f3d0c750d1dbd33bac52af552a7c (Feb 26)
swift-corelibs-foundation bb396c4886b162f9fe2220cbb543f8002e153e42 (Feb 10)

Newer versions of swift-corelibs-foundation suffered from the posix_spawnattr_t issue. With revisions after the fix I can locally reproduce this issue. Since CI reproduces it with current mainline swift as well, it seems to origin from swift-corelibs-foundation or a combination of repos.

[weliveindetail]

Let's see if swiftlang/swift-corelibs-foundation#5180 is effective.

swiftlang/swift-testing#944
@swift-ci please test Windows

[weliveindetail]

Update checkout failed. Let's try again.

swiftlang/swift-testing#944
@swift-ci please test Windows

[weliveindetail]

bisect shows that #79588 caused this issue

...
bad   4c0e141ccce Merge pull request #79390 from al45tair/eng/PR-144497613
      42db3dc5392 Merge pull request #79590 from AnthonyLatsis/bubo-ascalaphus
bad   c539f7e11ac Merge pull request #79588 from xymus/ignore-more-swiftmodules
good  468371fe55e Merge pull request #79586 from nate-chandler/rdar145035291
      bb65b08b39c Merge pull request #79561 from compnerd/structure
good  f5dd557307b Merge pull request #79506 from drexin/wip-145095088
      71abe6f26b1 [Tests] Disable backtracing in some tests.
...

[weliveindetail]

Test the workaround and see if we hit cmp0157 in swift-testing

@swift-ci please test Windows

[weliveindetail]

They aren't installed yet. Delete them from the build-tree and try again.

@swift-ci please test Windows

[weliveindetail]

The issue is tracked now in #79839