Swiftbuild system doesn't support the build `--enable-parseable-module-interfaces` flag

[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

This flag triggers the native build system to produce .swiftinterface files. However, it doesn't do that with the swiftbuild build system.

Expected behavior

It is expected that the swiftbuild build system should be able to support this flag and produce the parsable interface files like the native build system.

Actual behavior

The build doesn't produce any interface files. See the test case for the details of the expected interface files.

Steps to reproduce

To reproduce on macOS with #8333

1. Edit Tests/CommandsTests/BuildCommandTests.swift to comment out the skipping of a test ~ line 859
2. Run the following test

swift test --filter=BuildCommandSwiftBuildTests.testParseableInterfaces

3. Ensure that the test is not being skipped

Swift Package Manager version/commit hash

main

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

Apple Swift version 6.0.3 (swift-6.0.3-RELEASE)
Target: arm64-apple-macosx15.0

[cmcgee1024]

There is a build setting called BUILD_FOR_DISTRIBUTION that should enable this capability with swift-build.

[cmcgee1024]

Note that a very similar situation happens when a Package.swift has set -enable-library-evolution as an unsafe flag. It could be a similar root cause.