[CMake] Update dependencies for CloudKit for Apple-internal configs.

rdar://problem/30432611

Author: jrose-apple

stdlib/public/SDK/CloudKit/CMakeLists.txt

@@ -4,10 +4,19 @@ add_swift_library(swiftCloudKit ${SWIFT_SDK_OVERLAY_LIBRARY_BUILD_TYPES} IS_SDK_
   SWIFT_COMPILE_FLAGS "${SWIFT_RUNTIME_SWIFT_COMPILE_FLAGS}"
   LINK_FLAGS "${SWIFT_RUNTIME_SWIFT_LINK_FLAGS}"
   TARGET_SDKS ALL_APPLE_PLATFORMS
+
+  # The dependency on the 'os' module only appears in particular Apple-internal
+  # configurations, but it causes no harm to specify it unconditionally.
+  # The ./utils/find-overlay-dependencies.sh tool only touches the
+  # OSX|IOS|TVOS|WATCHOS lines, so the standalone "os" lines remain.
   SWIFT_MODULE_DEPENDS_OSX Darwin Contacts CoreGraphics CoreLocation Dispatch Foundation IOKit ObjectiveC # auto-updated
+    os
   SWIFT_MODULE_DEPENDS_IOS Darwin Contacts CoreLocation Dispatch Foundation ObjectiveC # auto-updated
+    os
   SWIFT_MODULE_DEPENDS_TVOS Darwin CoreLocation Dispatch Foundation ObjectiveC # auto-updated
+    os
   SWIFT_MODULE_DEPENDS_WATCHOS Darwin CoreLocation Dispatch Foundation ObjectiveC # auto-updated
+    os
   FRAMEWORK_DEPENDS_WEAK CloudKit
 
   DEPLOYMENT_VERSION_OSX ${SWIFTLIB_DEPLOYMENT_VERSION_CLOUDKIT_OSX}