The Apple SDKs have been providing the Darwin overlay since macOS 10.14.4, iOS 12.2, et al. More recently the SDK version has diverged from the Swift version making them incompatible. Stop building the overlay from Swift. Once the SDK overlays aren't being built, the clang overlays need to be built in testing.
rdar://115192929
The Apple SDKs have been providing the Darwin overlay since macOS 10.14.4, iOS 12.2, et al. More recently the SDK version has diverged from the Swift version making them incompatible. Stop building the overlay from Swift. Once the SDK overlays aren't being built, the clang overlays need to be built in testing.
%target-swift-emit-pcm doesn't use the sdk, but %target-swift-frontend does, which will cause them to have a mismatch with "builtin headers belong to system modules, and _Builtin_ modules are ignored for cstdlib headers" aka LANGOPT(BuiltinHeadersInSystemModules) aka -fbuiltin-headers-in-system-modules.
rdar://115192929
