Error while building SwiftPM library with Windows: "lld-link: error: subsystem must be defined"

[cmcgee1024]

Is it reproducible with SwiftPM command-line tools: swift build, swift test, swift package etc?

• Confirmed reproduction steps with SwiftPM CLI. The description text must include reproduction steps with either of command-line SwiftPM commands, swift build, swift test, swift package etc.

Description

SwiftPM libraries are failing to build with the swiftbuild build system with this error when building on Windows x86.

Expected behavior

The package should build without error on Windows x86.

Actual behavior

The package fails to build with the linker error: "lld-link: error: subsystem must be defined".

Steps to reproduce

• Clone the latest SwiftPM on the main branch
• Create a simple library package using the init function:

emptydir=$(mktemp -d)
(cd "$emptydir"; swift package init --type=library)

• Build the project with the swiftbuild build system

swift run swift-build --package-path="$emptydir" --build-system=swiftbuild

See also this test: BuildPlanSwiftBuildTests.testPackageNameFlag (related to #8433).

Swift Package Manager version/commit hash

main

Swift & OS version (output of swift --version ; uname -a)

6.2-dev Windows x86_64

[cmcgee1024]

See swiftlang/swift-build#310

This could be related: swiftlang/swift-build#104

[dschaefer2]

Let's move the discussion to swiftlang/swift-build#310.