C Settings are not propagated to consuming modules

[dschaefer2]

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

Often C settings affect the interface of the C module and flags and include paths need to be propagated to consuming modules in order for the interface to compile properly.

This should be automatic.

swift-java is a great example of that.

Also we're seeing symbol warnings in SwiftPM build on Windows because the CYaml flags aren't propagated.

Expected behavior

No response

Actual behavior

No response

Steps to reproduce

No response

Swift Package Manager version/commit hash

No response

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

No response

[dschaefer2]

Duplicate of #8077