Unable to resolve build file errors when build universal binaries for macOS with swiftbuild build system

[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

When building swiftly as a macOS universal binary (x86_64 with arm64) with the swiftbuild build system there are multiple errors related to resolving build files.

Build description signature: e94cb578192cef8329eaceffc7c03695
Build description path: /Users/cmcgee/git/swiftly-public/.build/apple/Intermediates.noindex/XCBuildData/e94cb578192cef8329eaceffc7c03695.xcbuilddata
Unable to resolve build file: BuildFile<PACKAGE-PRODUCT:test-swiftly::BUILDPHASE_1::7>
(The workspace has a reference to a missing target with GUID Unable to resolve build file: BuildFile<PACKAGE-PRODUCT:test-swiftly::BUILDPHASE_1::7>
(The workspace has a reference to a missing target with GUID Unable to resolve build file: BuildFile<PACKAGE-PRODUCT:build-swiftly-release::BUILDPHASE_1::7>
(The workspace has a reference to a missing target wUnable to resolve build file: BuildFile<PACKAGE-PRODUCT:build-swiftly-release::BUILDPHASE_1::7>
(The workspace has a reference to a missing target wUnable to resolve build file: BuildFile<PACKAGE-PRODUCT:swiftly::BUILDPHASE_1::8>
(The workspace has a reference to a missing target with GUID 'PACKUnable to resolve build file: BuildFile<PACKAGE-PRODUCT:swiftly::BUILDPHASE_1::8>
(The workspace has a reference to a missing target with GUID 'PACKAGE-TARGET:GenerateCommandModels@11')
Build failed

Expected behavior

It is expected that the build will succeed and there will be a universal binary for swiftly.

Actual behavior

No response

Steps to reproduce

1. Checkout the main branch of SwiftPM
2. Do a swiftly package update to get the latest swift-build
3. Checkout the main branch of swiftly https://github.com/swiftlang/swiftly into a different directory
4. From SwiftPM directory run swift run swift-build --package-path <path_to_swiftly> --buildsystem swiftbuild --arch arm64 --arch x86_64

Swift Package Manager version/commit hash

main

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

macOS Sequoia 15.5

[owenv]

It looks like multi-arch builds are forcing us into --build-system Xcode mode still even if we explicitly specify --build-system swiftbuild

[dschaefer2]

Yup, noticed that too.