Intermittent warning about liburing_nio.h not being included by CNIOLinux

[gwynne]

Expected behavior

Building a project which includes NIO should not produce warnings.

Actual behavior

Regardless of whether building in Xcode or commandline on macOS, or on Linux, the following warning sometimes appears (most often in clean builds). I have not observed any consistency to when it does or does not appear. This transcript is from an occurrence during a clean build in Xcode:

<module-includes>:1:9: note: in file included from <module-includes>:1:
1 | #import "/Users/gwynne/Library/Developer/Xcode/DerivedData/vapor-queues-fluent-driver-bcagwcjtvkaedacdjohngzbxgbvx/SourcePackages/checkouts/swift-nio/Sources/CNIOLinux/include/CNIOLinux.h"
  |         `- note: in file included from <module-includes>:1:
2 | 

/Users/gwynne/Library/Developer/Xcode/DerivedData/vapor-queues-fluent-driver-bcagwcjtvkaedacdjohngzbxgbvx/SourcePackages/checkouts/swift-nio/Sources/CNIOLinux/include/CNIOLinux.h: 0:
/Users/gwynne/Desktop/Vapor/vapor-queues-fluent-driver/.swiftpm/xcode/<module-includes>:1:9: In file included from <module-includes>:1:

/Users/gwynne/Library/Developer/Xcode/DerivedData/vapor-queues-fluent-driver-bcagwcjtvkaedacdjohngzbxgbvx/SourcePackages/checkouts/swift-nio/Sources/CNIOLinux/include/CNIOLinux.h:138:1: Umbrella header for module 'CNIOLinux' does not include header 'liburing_nio.h'

Steps to reproduce

1. Clean-build any project with a dependency on SwiftNIO 2.66.0.
2. The warning does not always appear; it may take multiple attempts.

SwiftNIO version/commit hash

SwiftNIO tag 2.66.0

System & version information

Most recent reproducer was on:

$ sw_vers
ProductName:        macOS
ProductVersion:     14.5
BuildVersion:       23F79

$ xcodebuild -version
Xcode 15.4
Build version 15F31c

$ swift --version
swift-driver version: 1.90.11.1 Apple Swift version 5.10 (swiftlang-5.10.0.13 clang-1500.3.9.4)
Target: arm64-apple-macosx14.0

[Lukasa]

I agree, please feel free to add this to the umbrella header.