Module not found diagnostics are repeated multiply

[compnerd]

When a module is not found, the warning is emitted multiple times leading to an overwhelming amount of spew when it is a core module (e.g. _SwiftConcurrencyShims).

warning: (x86_64) S:\tmp\ARCFoundationPackageTests.xctest 0x003772fd: unable to locate module needed for external types: C:\workspace\arc\Frameworks\ARCFoundation\.build\x86_64-unknown-windows-msvc\debug\ModuleCache\3L5Z3Z5BE6NFH\_SwiftConcurrencyShims-36FOFAYY5BS9A.pcm
error: 'C:\workspace\arc\Frameworks\ARCFoundation\.build\x86_64-unknown-windows-msvc\debug\ModuleCache\3L5Z3Z5BE6NFH\_SwiftConcurrencyShims-36FOFAYY5BS9A.pcm' does not exist
Debugging will be degraded due to missing types. Rebuilding the project will regenerate the needed module files.

This error was emitted 100s of times (beyond the scope of the terminal scrollback).